Stratix GX Transceiver User Guide
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UG-STXGX-3.0 P25-10021-02 Copyright © 2005 Altera Corporation. All rights reserved. Altera, The Programmable Solutions Company, the stylized Altera logo, specific device des- ignations, and all other words and logos that are identified as trademarks and/or service marks are, unless noted otherwise, the trademarks and service marks of Altera Corporation in the U.S. and other countries. All other product or service names are the property of their respective holders. Al- tera products are protected under numerous U.S. and foreign patents and pending applications, maskwork rights, and copyrights. Altera warrants performance of its semiconductor products to current specifications in accordance with Altera's standard warranty, but reserves the right to make changes to any products and services at any time without notice. Altera assumes no responsibility or liability arising out of the ap- plication or use of any information, product, or service described herein except as expressly agreed to in writing by Altera Corporation. Altera customers are advised to obtain the latest version of device specifications before relying on any published in- formation and before placing orders for products or services.
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ii Altera Corporation Contents
About This User Guide ...... vii How to Contact Altera ...... vii Typographic Conventions ...... viii
Chapter 1. Introduction Gigabit Transceiver Block Highlights ...... 1–1 Transceiver Block Architecture ...... 1–2 Analog Section Overview ...... 1–2 Digital Overview ...... 1–3 Modes of Operation ...... 1–5 Basic Mode ...... 1–5 SONET Mode ...... 1–6 XAUI Mode ...... 1–7 GigE Mode ...... 1–8 Loopback ...... 1–9 Built-In Self Test ...... 1–9
Chapter 2. Stratix GX Analog Description Introduction ...... 2–1 Transmitter Analog ...... 2–2 Transmitter Buffer ...... 2–2 Transmitter PLL ...... 2–5 Serializer (Parallel-to-Serial Converter) ...... 2–8 Receiver Analog ...... 2–9 Receiver Input Buffer ...... 2–9 Receiver PLL ...... 2–12 Clock Recovery Unit ...... 2–16 Deserializer (Serial-to-Parallel Converter) ...... 2–19 MegaWizard Analog Features ...... 2–20 MegaWizard Analog Feature Considerations ...... 2–20
Chapter 3. Basic Mode Introduction ...... 3–1 Basic Mode Receiver Architecture ...... 3–2 Word Aligner ...... 3–2 8B/10B Decoder ...... 3–9 Byte Deserializer ...... 3–13 Receiver Phase Compensation FIFO Buffer ...... 3–15 Basic Mode Transmitter Architecture ...... 3–16 Transmitter Phase Compensation FIFO Buffer ...... 3–16
Altera Corporation iii
Contents Stratix GX Transceiver User Guide
Byte Serializer ...... 3–17 8B/10B Encoder ...... 3–17 Basic Mode Clocking ...... 3–20 Basic Mode Channel Clocking ...... 3–20 Basic Mode Inter-Transceiver Block Clocking ...... 3–24 Basic Mode MegaWizard Plug-In ...... 3–29 Basic Mode MegaWizard Plug-In Manager Considerations ...... 3–29 Basic Mode altgxb MegaWizard Options ...... 3–29
Chapter 4. SONET Mode Introduction ...... 4–1 SONET Mode Receiver Architecture ...... 4–2 Word Aligner ...... 4–2 Byte Deserializer ...... 4–8 Receiver Phase Compensation FIFO Module ...... 4–10 SONET Mode Transmitter Architecture ...... 4–11 Transmitter Phase Compensation FIFO Buffer ...... 4–11 Byte Serializer ...... 4–12 SONET Mode Clocking ...... 4–12 SONET Mode Channel Clocking ...... 4–12 SONET Mode Inter-Transceiver Block Clocking ...... 4–17 SONET Mode MegaWizard Plug-In Manager ...... 4–23 SONET Mode MegaWizard Considerations ...... 4–23 SONET Mode altgxb MegaWizard Options ...... 4–23
Chapter 5. XAUI Mode Introduction ...... 5–1 XAUI Mode Receiver Architecture ...... 5–5 Word Aligner ...... 5–6 Channel Aligner ...... 5–9 Rate Matcher ...... 5–11 8B/10B Decoder ...... 5–11 PCS - XGMII Code Conversion ...... 5–15 Byte Deserializer ...... 5–15 Receiver Phase Compensation FIFO Module ...... 5–18 XAUI Mode Transmitter Architecture ...... 5–18 Transmitter Phase Compensation FIFO Module ...... 5–18 Byte Serializer ...... 5–19 XGMII Character to PCS Code-Group Mapping ...... 5–20 8B/10B Encoder ...... 5–21 XAUI Mode Clocking ...... 5–24 XAUI Mode Channel Clocking ...... 5–24 XAUI Inter-Transceiver Block Clocking ...... 5–28 XAUI Mode MegaWizard Plug-In Manager ...... 5–34 XAUI Mode MegaWizard Considerations ...... 5–34 XAUI Mode altgxb MegaWizard Options ...... 5–34
iv Altera Corporation
Contents Contents
Chapter 6. GigE Mode Introduction ...... 6–1 Word Aligner ...... 6–4 Rate Matcher ...... 6–9 8B/10B Decoder ...... 6–11 Receiver Phase Compensation FIFO Buffer ...... 6–14 GigE Mode Transmitter Architecture ...... 6–14 Transmitter Phase Compensation FIFO Buffer ...... 6–15 GigE Transmitter Synchronization ...... 6–16 Idle Generation ...... 6–16 8B/10B Encoder ...... 6–17 GigE Mode Clocking ...... 6–20 GigE Mode Channel Clocking ...... 6–20 GigE Mode Inter-Transceiver Clocking ...... 6–25 GigE Mode MegaWizard Considerations ...... 6–31 GigE Mode altgxb MegaWizard Options ...... 6–31 Design Example ...... 6–38 Design Description ...... 6–38 Simulation Waveform & Hardware Verification Results ...... 6–44
Chapter 7. Loopback Modes Introduction ...... 7–1 Serial Loopback ...... 7–1 Parallel Loopback ...... 7–2 Reverse Serial Loopback ...... 7–3
Chapter 8. Stratix GX Built-In Self Test (BIST) Introduction ...... 8–1 Pattern Generator ...... 8–2 PRBS Mode Generator ...... 8–2 Incremental Mode Generator ...... 8–3 High-Frequency Mode Generator ...... 8–3 Low-Frequency Mode Generator ...... 8–4 Mix-Frequency Mode Generator ...... 8–5 Pattern Verifier ...... 8–5 PRBS Mode Verifier ...... 8–5 Incremental Mode Verifier ...... 8–6 Design Examples ...... 8–7 Design 1: PRBS BIST Generator & Verification Design ...... 8–7 Design 2: Incremental BIST Generator & Verification Design ...... 8–11 Design 3: High-Frequency Transmitter Generator Design ...... 8–16 Design 4: Low-Frequency Transmitter Generator Design ...... 8–18 Design 5: Mix-Frequency Transmitter Generator Design ...... 8–20
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Contents Stratix GX Transceiver User Guide
Chapter 9. Reset Control & Power Down Introduction ...... 9–1 Power On Reset (POR) ...... 9–1 USER Reset & Enable Signals ...... 9–1 Recommended Resets ...... 9–4 Receiver & Transmitter Reset ...... 9–4 Receiver Reset ...... 9–32 Transmitter Reset ...... 9–52 Power Down ...... 9–57
Appendix A. Data & Control Codes 8B/10B Code ...... A–1 Code Notation ...... A–1 Disparity Calculation ...... A–1 Supported Codes ...... A–3
Appendix B. Ports & Parameters Input Ports ...... B–1 Output Ports ...... B–5 Parameter Descriptions ...... B–9
Appendix C. REFCLKB Pin Constraints Known Issues ...... C–1 Quartus II Software Messages ...... C–3 Recommendations ...... C–5
vi Altera Corporation
About This User Guide
How to Contact For the most up-to-date information about Altera® products, go to the Altera world-wide web site at www.altera.com. For technical support on Altera this product, go to www.altera.com/mysupport. For additional information about Altera products, consult the sources shown below.
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Altera Corporation vii Preliminary Typographic Conventions Stratix GX Transceiver User Guide
Typographic This document uses the typographic conventions shown below. Conventions
Visual Cue Meaning Bold Type with Initial Command names, dialog box titles, checkbox options, and dialog box options are Capital Letters shown in bold, initial capital letters. Example: Save As dialog box. bold type External timing parameters, directory names, project names, disk drive names, filenames, filename extensions, and software utility names are shown in bold type. Examples: fMAX, \qdesigns directory, d: drive, chiptrip.gdf file. Italic Type with Initial Capital Document titles are shown in italic type with initial capital letters. Example: AN Letters 75: High-Speed Board Design. Italic type Internal timing parameters and variables are shown in italic type. Examples: tPIA, n + 1.
Variable names are enclosed in angle brackets (< >) and shown in italic type. Example:
Anything that must be typed exactly as it appears is shown in Courier type. For example: c:\qdesigns\tutorial\chiptrip.gdf. Also, sections of an actual file, such as a Report File, references to parts of files (e.g., the AHDL keyword SUBDESIGN), as well as logic function names (e.g., TRI) are shown in Courier. 1., 2., 3., and Numbered steps are used in a list of items when the sequence of the items is a., b., c., etc. important, such as the steps listed in a procedure. ■ ● • Bullets are used in a list of items when the sequence of the items is not important. v The checkmark indicates a procedure that consists of one step only. 1 The hand points to information that requires special attention. r The angled arrow indicates you should press the Enter key. f The feet direct you to more information on a particular topic.
viii Altera Corporation Preliminary 1. Introduction
Introduction Stratix® GX devices combine highly advanced 3.1875-gigabit-per-second (Gbps) four-channel gigabit transceiver blocks with one of the industry’s most advanced FPGA architectures. Stratix GX devices are manufactured on a 1.5-V, 0.13-µm, all-layer copper CMOS process technology with 1.5- V PCML I/O standard support.
Historically, designers have used high-speed transceivers in strictly structured, line-side applications. Now, with the new gigabit transceiver blocks embedded in FPGAs, you can use transceivers in a host of new systems that require flexibility, increased time-to-market, high performance, and top-of-the-line features.
Gigabit Stratix GX devices are organized into four-channel blocks with four 3.1875 Gbps full-duplex channels per block and up to 20 channels (in five Transceiver blocks) per device. Each self-contained Stratix GX gigabit transceiver Block Highlights block supports a variety of embedded functions and does the following: ■ Supports frequencies from 500 megabits per second (Mbps) to 3.1875 Gbps ■ Integrates serializer/deserializer (SERDES), clock data recovery (CDR), word aligner, channel aligner, rate matcher, 8B/10B encoder/decoder, byte serializer/deserializer, and phase compensation first-in first-out (FIFO) modules ■ Supports flexible reference clock generation capabilities, including a dedicated transmitter phase-locked loop (PLL) and four receiver PLLs per gigabit transceiver block ■ Supports programmable pre-emphasis, equalization, and programmable VOD settings in I/O buffers, and dynamic reprogrammability for each of these features ■ Implements XAUI physical media attachment (PMA) and physical coding sublayer (PCS) functionality for 10GBASE-X systems ■ Provides built-in Gigabit Ethernet (GigE) physical coding sublayer functionality ■ Provides individual transmitter and receiver power-down capability for reduced power consumption during non-operation ■ Includes built-in self test (BIST) capability, including embedded Pseudo Random Binary Sequence (PRBS) pattern generation and verification ■ Includes three independent loopback paths for system verification
Altera Corporation 1–1 January 2005 Transceiver Block Architecture
Transceiver Figure 1–1 shows a block diagram of the gigabit transceiver block (GXB). You can bypass various modules if desired. Refer to“Modes of Block Operation” on page 1–5 for a description of the supported features in Architecture each mode. You can divide the transceiver block into an analog section and a digital section, as shown in Figure 1–1.
Figure 1–1. Block Diagram of a Stratix GX Gigabit Transceiver Block
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner Clock Matcher 8B/10B FIFO Buffer Decoder Byte Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
Analog Section Overview
This section describes the various components within the analog section of the transceiver block.
Transmitter Differential I/O Buffers The gigabit transmitter block differential I/O buffers support the 1.5-V PCML I/O standard, and contain features that improve system signal integrity. These features include programmable pre-emphasis, which helps compensate for high frequency losses, and a variety of programmable VOD settings that support noise margin tuning.
Receiver Differential I/O Buffers The gigabit transceiver block differential I/O buffers support the 1.5-V PCML I/O standard, and contain a variety of features that improve system signal integrity. Programmable equalization capabilities are used to compensate for signal degradation across transmission mediums.
1–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Introduction
Transmitter & Receiver PLLs Each gigabit transceiver block contains one dedicated transmitter PLL and four dedicated receiver PLLs. These PLLs provide clocking flexibility and support a range of incoming data streams. For data transmission and recovery, these PLLs generate the required clock frequencies based upon the synthesis of an input reference clock. Each transmitter PLL supports multiplication factors of 2, 4, 5, 8, 10, 16, or 20. Either external reference clocks or a variety of clock sources within the Stratix GX device drive the PLLs.
Clock Recovery Unit The gigabit transceiver block clock recovery unit (CRU) performs analog Clock Data Recovery (CDR). The CRU uses an external reference clock to extract a recovered clock that is frequency and phase aligned with the incoming data, thereby eliminating any clock-to-data skew. This recovered clock then clocks the data through the rest of the gigabit transceiver block.
Serializer Deserializer (SERDES) The transmitter serializer converts the incoming lower speed parallel signal to a high-speed serial signal on the transmit side. The SERDES supports a variety of conversion factors, ensuring implementation flexibility. For example, the SERDES supports 10- and 20-bit serialization factors, typically required for 8B/10B encoded data, as well as 8- and 16-bit factors.
The receiver deserializer converts the incoming data stream from a high-speed serial signal to a lower-speed parallel signal that can be processed in the FPGA logic array on the receive side. The SERDES supports a variety of conversion factors, ensuring implementation flexibility. For example, the SERDES supports both 10-bit and 8-bit serialization and deserialization factors.
Digital Overview
This section describes the various components in the digital section of the transceiver block.
Altera Corporation 1–3 January 2005 Stratix GX Transceiver User Guide Transceiver Block Architecture
Transmitter & Receiver Phase Compensation FIFO Buffer The transmitter and receiver data path has a dedicated phase compensation FIFO buffer that decouples phase variations between the FPGA and transceiver clock domains. These FIFO buffers ensure a consistent, reliable interface to the logic array and simplify system design and timing analysis.
Byte Serializer/Deserializer The byte serializer converts a 16- or 20-bit data bus into two 8- or 10-bit data buses, respectively, at double the data rate. The byte serializer converts an 8- or 10-bit data bus into 16- or 20-bit data buses, allowing maximum throughput of the transceiver without burdening the FPGA logic array.
The byte deserializer converts an 8- or 10-bit data bus into 16- or 20-bit data buses, allowing maximum throughput of the transceiver without burdening the FPGA logic array.
8B/10B Encoder/Decoder 8B/10B encoding/decoding is the backbone of many transceiver protocols, and it is often used in proprietary implementations. The gigabit transceiver block has dedicated circuitry to perform 8B/10B encoding in the transmitter and decoding in the receiver. This coding technique ensures sufficient data transitions and a DC balanced stream in the data signal for successful data recovery at the receiver.
Word Aligner The word aligner module contains a fully programmable pattern detector to identify specific patterns within the incoming data stream. The pattern detector includes recognition support /K28.5/ comma characters for 8B/10B encoded data and A1 or A2 frame alignment patterns for scrambled signals. Additionally, you can specify a custom alignment pattern in lieu of the /K28.5/ comma.
The word aligner in the gigabit transceiver block also creates words from the incoming serial data stream by realigning the data based on identified byte boundaries. The realignment function uses a barrel shifter and works with the pattern detector. Additionally, the word aligner has a manual data realignment mode that lets you control the data realignment in user mode without consistent alignment characters.
1–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Introduction
Channel Aligner An embedded channel aligner aligns byte boundaries across multiple channels and synchronizes the data entering the logic array from the gigabit transceiver block’s four channels. The Stratix GX channel aligner is optimized for a 10-Gigabit Ethernet XAUI 4-channel implementation. The channel aligner includes the control circuitry and channel alignment character detection defined by the XAUI protocol. The channel aligner is only available in XAUI mode.
Rate Matcher In multi-crystal environments, the clock frequencies of the transmitting and receiving devices do not match. This mismatch can cause the data to transmit at a rate slightly faster or slower than the receiving device can interpret. The Stratix GX rate matcher resolves the frequency differences between the recovered clock and the FPGA logic array clock by inserting or deleting removable characters from the data stream, as defined by the transmission protocol, without compromising transmitted data. If the functional mode is XAUI, the rate matcher is based on the 10-Gigabit Ethernet protocol. If the functional mode is GigE, the rate matcher is based on the Gigabit Ethernet protocol.
Modes of You can bypass various modules of the gigabit transceiver block based on the configured mode of operation. Stratix GX transceivers currently Operation support basic mode, SONET mode, and XAUI mode. This section provides an overview of each supported mode of operation.
Basic Mode
Basic mode enables a subset of the transceiver blocks so you can perform customizable configuration. Channel aligner and the rate matcher features are not available in this mode. Refer to the Basic Mode chapter for more details on the configurability of this mode. Figure 1–2 shows a block diagram of a duplex channel configured in basic mode.
Altera Corporation 1–5 January 2005 Stratix GX Transceiver User Guide Modes of Operation
Figure 1–2. Block Diagram of a Duplex Channel Configured in Basic Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
SONET Mode
SONET mode lets you to select a subset of the transceiver blocks to perform SONET-like configuration. SONET-like implies that the data width can either be 8 or 16 bits and that the 8B/10B encoder/decoder, channel aligner, and the rate matcher features are not available. Refer to the SONET Mode chapter for more details on the configurability of this mode. Figure 1–3 shows a block diagram of a duplex channel configured in SONET mode.
1–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Introduction
Figure 1–3. Block Diagram of a Duplex Channel Configured in SONET Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
XAUI Mode
Stratix GX transceivers contain embedded macros dedicated to supporting the XAUI protocol, specified in clause 47 of the IEEE 802.3ae specification. These macros includes synchronization, channel deskew, rate matching, XGXS to XGMII, and XGMII to XGXS code-group conversion. Refer to the XAUI Mode chapter for more details on the configurability of this mode. Figure 1–4 shows a block diagram of a duplex channel configured in XAUI mode.
Altera Corporation 1–7 January 2005 Stratix GX Transceiver User Guide Modes of Operation
Figure 1–4. Block Diagram of a Duplex Channel Configured in XAUI Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner Clock Matcher 8B/10B FIFO Buffer Decoder Byte Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
GigE Mode
Stratix GX devices in GigE mode can use the 8B/10B encoder/decoder, rate matcher, synchronizer, and byte serializer/deserializer built-in hard macros. Refer to the GigE Mode chapter for more information about this mode. The rate matcher and word aligner each have a dedicated state machine governing their functions. These state machines are active only in GigE mode. Figure 1–5 shows a block diagram of a duplex channel configured in GigE mode.
1–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Introduction
Figure 1–5. Block Diagram of a Duplex Channel Configured in GigE Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
Loopback
There are three different loopback modes to use in the gigabit transceiver block to allow for a complete method of in-system verification. The loopback modes are versatile and robust enough to accommodate all protocols and let you to choose whether to retime the data.
Built-In Self Test
The gigabit transceiver block contains several features that simplify design verification. An embedded PRBS pattern generator provides a bitstream pattern that you can use to test the device and board connections. The PRBS pattern generator works with a PRBS receiver to implement a full self-test path. Additionally, serial and parallel loopback paths let you test the FPGA logic without monitoring external signals. The reverse loopback path enables external system testing with minimal device interaction.
Altera Corporation 1–9 January 2005 Stratix GX Transceiver User Guide Modes of Operation
1–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 2. Stratix GX Analog Description
Introduction This chapter describes how to serialize the parallel data for transmission and convert received data into parallel data. Data transmission and reception is performed by pseudo current mode logic (PCML) buffers. These transceiver buffers support programmable pre-emphasis, equalization, and programmable VOD settings in I/O buffers.
The programmable pre-emphasis setting is available on transmit buffers to maximize the eye opening on the far-end receiver by boosting the high-frequency component of the data signal. Similarly, programmable equalization is available for receive buffers to reduce the high-frequency losses and inter-symbol interference. These features are useful in lossy transmission lines. Transceivers also support flexible reference clock generation capabilities, including a dedicated transmitter phase-locked loop (PLL) and four receiver PLLs per transceiver block.
The clock recovery unit (CRU) is the main part of each receive analog section; it recovers the clock from the serial data stream (see Figure 2–1).
You can set the CRU to automatically or manually alter the receiver PLL phase and frequency to match the bit transition on the incoming data stream. This is to eliminate any clock-to-data skew or to keep the receiver PLL locked to the reference clock (lock-to-data or lock-to-reference mode).
During the clock recovery phase, the receiver PLL initially locks to the reference clock and then attempts to lock on to the incoming data by first recovering the clock from the incoming serial data.
Altera Corporation 2–1 January 2005 Transmitter Analog
Figure 2–1. Block Diagram Analog Components
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
Transmitter This section describes the transmitter buffer, the transmitter PLL, and the Analog serializer. Figure 2–2 shows the transmitter analog components.
Figure 2–2. Transmitter Analog Components
Analog Section Digital Section
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Transmitter
Transmitter Buffer
The Stratix® GX transceiver buffers support the 1.5-V PCML standard at speeds up to 3.1875 gigabits per second (Gbps) and are capable of driving 40 inches of FR4 trace across two connectors. In addition, the buffer contains programmable output voltage, programmable pre-emphasis circuitry, and internal termination circuitry.
2–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Programmable Voltage Output Differential (VOD) Stratix GX transceivers let you customize the differential output voltage (VOD) to handle different length, backplane, and receiver requirements (see Figure 2–3). You can select the VOD (differential) from a range of 400 to 1,600 mV, as shown in Table 2–1.
Figure 2–3. VOD (Differential) Signal Level
Single-Ended Waveform
Positive Channel (p) = VOH
VOD
Negative Channel (n) = VOL VCM Ground
Differential Waveform (VOD (Differential) = 2 x VOD (single-ended))
VOD p − n = 0 V
VOD
Table 2–1 shows the differential output voltage (VOD) setting per current level for each of the on-chip transmitter programmable termination values.
Table 2–1. Programmable VOD (Differential)
100 Ω (mV) 120 Ω (mV) 150 Ω (mV) 400 480 600 800 960 1,200 1,000 1,200 1,500 1,200 1,440 1,400 1,600
Altera Corporation 2–3 January 2005 Stratix GX Transceiver User Guide Transmitter Analog
You can set the differential VOD values statically during configuration or dynamically adjust them in user mode. You select the static VOD value through a list in the altgxb MegaWizard® Plug-In Manager, which sets the appropriate VOD setting in the configuration file. The disadvantage of the static mode setting is that the VOD is set on a per transceiver block basis and cannot be changed unless you regenerate another programming file.
Alternatively, if you enable dynamic adjustment in the altgxb MegaWizard Plug-In, you can dynamically configure the VOD setting by the device during user mode. This configuration is done by asserting encoded values on the tx_vodctrl bus, which is instantiated in the altgxb module when you select the dynamic adjustment option. This option lets you make quick performance evaluations of the various settings without having to recompile and regenerate multiple configuration files. Another advantage of this option is that it allows the VOD of each channel to be configured independently. Refer to the section “MegaWizard Analog Features” on page 2–20 for further details.
Programmable Pre-Emphasis The programmable pre-emphasis module in each transmit buffer boosts the high frequencies in the transmit data signal, which may be attenuated in the transmission media. This maximizes the data eye opening at the far-end receiver. Pre-emphasis is particularly useful in lossy transmission mediums.
The transfer function of a transmission line can be represented in the frequency domain as a low-pass filter. Any frequency components below the –3 dB frequency pass through with minimal losses. Frequency components that are greater than the –3-dB frequency are attenuated. This variation in frequency response yields data-dependant jitter and other ISI effects. By applying pre-emphasis, the high frequency components are boosted, or in other words, pre-emphasized. This pre-emphasis equalizes the frequency response as seen at the receiver so that the delta between the low-frequency and high-frequency components is reduced, which in return minimizes the ISI effects from the transmission medium.
In Stratix GX transceivers, the programmable pre-emphasis settings can have one of six values (0 to 5). You should experiment with the pre-emphasis values to determine the optimal setting based on your system variables.
2–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
As with the VOD settings, you can set the pre-emphasis settings statically during configuration or adjust them dynamically in user mode. You can set the static pre-emphasis value through a drop-down menu in the altgxb MegaWizard Plug-In, which sets the appropriate pre-emphasis setting in the configuration file. The disadvantage of the static mode setting is that the pre-emphasis is set on a per-transceiver-block basis and cannot be changed without regenerating another programming file.
On the other hand, if you select dynamic adjustment in the altgxb MegaWizard Plug-In, the pre-emphasis setting can be configured dynamically by the device during user mode. This configuration is done by asserting encoded values on the tx_preemphasisctrl bus, which is instantiated in the altgxb module when you select the dynamic adjustment option. This option lets you make quick performance evaluations of the various settings without having to recompile and regenerate multiple configuration files. Another advantage of this option is that it allows the pre-emphasis of each channel to be configured independently. For further details, refer to “MegaWizard Analog Features” on page 2–20.
Avoid pre-emphasis and VOD settings that yield a value greater than 1,600 mV. Settings beyond this value do not damage the buffer, but they prevent accurate device operation. Verify that the combination of VOD and pre-emphasis settings do not exceed the 1,600-mV limit.
Programmable Transmitter Termination The Stratix GX transmitter buffer includes a 100-, 120-, or 150-Ω programmable on-chip differential termination resistor. The Stratix GX transmitter buffers are current-mode drivers, so the resultant VOD is a function of the transmitter termination value. For more information on resultant VOD values, see “Programmable Voltage Output Differential (VOD)” on page 2–3.
Transmitter PLL
Each transceiver block contains a transmitter PLL and a slow-speed reference clock. The transmitter PLL receives the reference clock and generates the high-speed serial clock used by the serializer. The slow- speed reference clock is used for the transceiver logic. Figure 2–4 shows the transmitter PLL’s block diagram. The pll_locked signal indicates when the transmitter PLL is locked to the reference clock. A high signal indicates that the PLL is locked to the reference clock; a low signal indicates that the PLL is not locked to the reference clock.
Altera Corporation 2–5 January 2005 Stratix GX Transceiver User Guide Transmitter Analog
Figure 2–4. Transmitter PLL Block Diagram
/4, 8, 10, 16, 20
/m
High Speed TX_PLL_CLK Clock Driver Low Speed TX_PLL_CLK Up Inter Quad Routing (IQ1) Inter Quad Routing (IQ0) INCLK PFD Down CP+LF VCO Global Clocks, I/O Bus, General Routing
Dedicated Local /2 REFCLKB
Table 2–2 lists some of the transmitter PLL specifications.
Table 2–2. Transmitter PLL Specifications
Parameter Specifications Input reference frequency range 25 MHz to 650 MHz Data rate support 500 Mbps to 3.1875 Gbps Multiplication factor (W) 2, 4, 5, 8, 10, 16, or 20 (1)
Note to Table 2–2: (1) Multiplication factors 2 and 5 can only be achieved with the use of the pre-divider on the REFCLKB.
Clock Synthesis The maximum input frequency of the phase frequency detector (PFD) is 325 MHz. To achieve reference clock frequency above this limitation, the /2 pre-divider on the dedicated local REFCLKB path can be enabled automatically by the Quartus® II software. The /2 pre-divider divides the reference clock frequency by a factor of 2 and then the /m factor compensates the frequency difference. An example would be a data rate of 2,488 Mbps with a 622-MHz reference clock. In this scenario, the reference clock must be assigned to the REFCLKB port where the 622- MHz reference clock is divided by 2, yielding a 311-MHz clock at the PFD. This 311-MHz reference clock is then multiplied by a factor of 8 to achieve the 2,488-MHz clock at the VCO.
2–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
If the reference clock exceeds 325 MHz, the clock must be fed by the dedicated local reference clock pin, REFCLKB. By default, the Quartus II software assigns pins to be LVTTL, so you must assign the 1.5-V PCML I/O standard to the I/O pins to select the REFCLKB port as the reference source. The Quartus II software prompts a fitter error if the reference clock exceeds 325 MHz and the reference clock source is not on the REFCLKB port.
You can also use the pre-divider on the REFCLKB path to support additional multiplication factors. The block diagram in Figure 2–4 shows that /m can only support multiplication factors of 4, 8, 10, 16, and 20, but Table 2–3 shows that the additional multiplication factors of 2 and 5 are also achievable. You can achieve these multiplication factors by using the pre-divider. A multiplication factor of 2 is achieved by pre-dividing the reference clock by 2 and then multiplying the resultant frequency by 4, which yields a multiplication factor of 2. A multiplication factor of 5 is achieved in the same manner by pre-dividing the reference clock by 2 and then multiplying the resultant frequency by 10, which yields a multiplication factor of 5.
Table 2–3 lists the possible multiplication values as a function of the source to the transmitter PLL. Table 2–3 assumes that the reference clock is directly fed from the source listed and does not factor any pre-clock synthesis (that is, the Stratix GX PLL driving a global clock that is used for the transmitter PLL reference clock source).
Table 2–3. Multiplication Values as a Function of the Reference Clock Source to the Transmitter PLL
Transmitter PLL Reference Clock Multiplication Factors Source Global clock, I/O bus, general routing 4, 8, 10, 16, 20 Inter-transceiver routing 2, 4, 5, 8, 10, 16, 20 Dedicated local REFCLKB 2, 4, 5, 8, 10, 16, 20
You must specify the data rate of the channel and input clock period of the reference clock. The data rate divided by the input clock period must equal one of the multiplication factors listed in Table 2–3.
Transmitter PLL Bandwidth Setting The Stratix GX transmitter PLL in the transceiver block offers a programmable bandwidth setting. The PLL bandwidth is the measure of its ability to track the input clock and jitter. The bandwidth is determined by the –3-dB frequency of the closed-loop gain of the PLL.
Altera Corporation 2–7 January 2005 Stratix GX Transceiver User Guide Transmitter Analog
A high-bandwidth setting provides a faster lock time and tracks more jitter on the input clock source which passes it through the PLL. This helps reject noise from the VCO and power supplies. A low-bandwidth setting, on the other hand, filters out more high frequency input clock jitter, but increases lock time.
You can set the bandwidth for Stratix GX devices to either low or high. The –3-dB frequencies for these settings can vary due to the non-linear nature and frequency dependencies of the circuit. As a result, you can vary the bandwidth to customize the performance on specific systems.
Serializer (Parallel-to-Serial Converter)
The serializer converts parallel data to serial data at the transmitter output buffer. The serializer can support 8- or 10-bit words when used with the transmitter multiplexer. The 8-bit serializer drives the serial data to the output buffer, as shown in Figure 2–5. The serializer can drive the serial bit-stream at a data rate range of 500 Mbps to 3.1875 Gbps. The serializer outputs the least significant bit (LSB) of the word first.
Figure 2–5. Example of 8-Bit Serialization
Serializer
D7 D7
D8 D8
D6 D6
D4 8 D4 Parallel Data D3 D3
D2 D2
D1 D1
Serial Data Out D0 D0 (I/O Output Buffer)
Low-Speed Parallel Clock High-Speed Serial Clock
Figure 2–6 shows the serial bit order of the serializer output. In this example, a constant 8’h6a (01010110) value is serialized.
1 The serial data is transmitted from LSB to most significant bit (MSB).
2–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Figure 2–6. Serializer Bit Order
Parallel Clock
Serial Clock
Parallel Data (in Hex) (x) 56
Serial Data Out 011 01 010
Receiver Analog This section describes the receiver input buffer, the receiver PLL, the clock recovery unit, and the deserializer. Figure 2–7 shows the receiver analog components.
Figure 2–7. Highlighted Block Diagram of the Receiver Analog Components
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Receiver
Receiver Input Buffer
The receiver input buffer contains internal termination and internal equalization. Figure 2–8 shows the structure of the input buffer. The input buffer has programmable equalization that you can apply to increase the signal integrity of the transmission line. The internal termination in the receiver buffer can support AC and DC coupling with programmable differential termination settings of 100, 120, or 150 Ω..
Altera Corporation 2–9 January 2005 Stratix GX Transceiver User Guide Receiver Analog
Figure 2–8. Receiver Input Buffer
Input Buffer
Programmable Termination
Programmable Input Pins Equalizer
To PLD Internal Loopback from Transmitter
Programmable Receiver Termination The Stratix GX receiver buffer includes programmable on-chip differential termination of 100, 120, or 150 Ω..
This assignment must be made per pin through the Assignment Editor in the Quartus II software. Select Assignment Organizer > Options for Individual Nodes Only > Stratix GX Termination Value (Assignments menu).
1 The proper termination settings should be selected and verified accordingly before compilation.
The transmitter PLL input signal (inclk) drives the termination resistance calibration circuit. The Quartus II software allows receiver-only configurations in Stratix GX devices. However, if you use the Quartus II software to remove the transmitter PLL in a receiver-only configuration, you will see an incorrect value or unpredictable behavior with the receiver input pin termination. If the rx_cruclk signal is globally routed, the Quartus II software handles this automatically. If the rx_cruclk signal is not globally routed or routed using the inter- quadrant line (IQ2), the Quartus II software returns a no-fit. In this situation, you must add a transmitter PLL to your design.
If the pll_areset (analog reset) signal goes high, the RX_Vcm value is less than the 1.1 V. This value varies unpredictably because the circuit is tristated. RX_Vcm is referenced from the Stratix GX receiver analog power supply.
2–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
If external termination is used, the receiver must be externally terminated and biased to 1.1 V. Figure 2–9 shows an example of an external termination and biasing circuit.
Figure 2–9. External Termination & Biasing Circuit
Receiver External Termination Stratix GX Device and Biasing
VDD 50/60/75-Ω Termination R1 Resistance C1 Receiver
R1/R2 = 1K RXIP × VDD {R2/(R1 + R 2)} = 1.1 V R2
RXIN
Receiver External Termination and Biasing
Transmission Line
Enable Stratix GX-to-Stratix GX Receiver DC Coupling You can configure the Stratix GX receiver buffers so that DC-coupled Stratix GX-to-Stratix GX communication is possible. The Stratix GX transmitter’s common-mode is typically around 750 mV, while the receiver common mode by default is approximately 1.1 V. However, by enabling DC coupling, the receiver common mode is biased to allow interoperability with the Stratix GX transmitter.
Equalizer Mode Stratix GX transceivers offer an equalization circuit in each receiver channel to increase noise margins and help reduce the effects of high frequency losses. The programmable equalizer compensates for inter-symbol interference (ISI) and high frequency losses that distort the signal and reduce the noise margin of the transmission medium by equalizing the frequency response.
The transfer function of a transmission line can be represented in the frequency domain as a low-pass filter. Any frequency components below the –3-dB frequency pass through with minimal losses. Frequency components that are greater than the –3-dB frequency are attenuated.
Altera Corporation 2–11 January 2005 Stratix GX Transceiver User Guide Receiver Analog
This variation in frequency response yields data-dependant jitter and other ISI effects. By applying equalization, the low frequency components are attenuated. This equalizes the frequency response so that the delta between the low frequency and high frequency components are reduced, which minimizes the ISI effects from the transmission medium.
In Stratix GX transceivers, the programmable equalizer settings can have one of five values (0 through four). You should experiment with the equalization values to determine the optimal setting based on your system variables.
As with the VOD settings, you can set the equalization settings statically during configuration or adjust them dynamically in user mode. You can select the static equalization value through a drop-down menu in the altgxb MegaWizard Plug-In. This action sets the appropriate equalization setting in the configuration file. The disadvantage of this mode is that the equalization is set on a per-transceiver block basis and cannot be changed without regenerating another programming file.
On the other hand, if you select the dynamic adjustment in the altgxb MegaWizard Plug-In, the equalization setting can be configured dynamically by the device during user mode. This configuration is accomplished by asserting encoded values on the rx_equalizerctrl signal, which is instantiated in the altgxb module when this option is selected. This feature lets you make quick performance evaluations of the various settings without having to recompile and regenerate multiple configuration files. Another advantage is that this option allows the equalization of each channel to be configured independently. Refer to “MegaWizard Analog Features” on page 2–20 for more details.
Receiver PLL
Each transceiver block contains four receiver PLLs and a slow-speed reference clock. The receiver PLLs receive the reference clock and generate the high-speed serial clock used by the CR. The slow-speed reference clock is used for the transceiver logic. Figure 2–10 shows the block diagram for the lock-to-reference portion of the receiver PLL.
This section focuses on the receiver PLL in Lock-to-Reference mode. The lock-to-data circuit has been omitted. Refer to the “Lock-to-Reference Mode & Lock-to-Data Mode” on page 2–16 for more information on the operation between the two modes.
2–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
The receiver PLL contains an optional loss-of-lock indicator signal (rx_locked) that indicates when the receiver PLL is not locked to the reference clock. The rx_locked signal is active low. A low signal indicates that the PLL is locked to a reference clock; a high signal indicates that the PLL is not locked to the reference clock.
Figure 2–10. Receiver PLL Block Diagram
÷m (1)
Low speed TX_PLL_CLK Up RX_CRUCLK PFD Inter Transceiver Block Routing Down Global Clks, I/O Bus, Gen Routing CP+LF VCO
Up
Dedicated Local Down ÷2 REFCLKB rx_locktorefclk rx_rlv[ ] rx_locktodata Clock Recovery Unit (CRU) High Speed RCVD_CLK RX_IN Low Speed RCVD_CLK
Note to Figure 2–10: (1) m = 8, 10, 16, or 20.
Table 2–4 lists some of the clock recovery unit specifications.
Table 2–4. Clock Recovery Unit Specifications
Parameter Specification Input reference frequency range 25 MHz to 650 MHz Data rate support 500 Mbps to 3.1875 Gbps Multiplication factor (W) 2, 4, 5, 8, 10, 16, or 20 (1)
Note to Table 2–4: (1) Multiplication factors 2, 4, and 5 can only be achieved with the use of the pre- divider on the REFCLKB port or if the CRU is trained with the low speed clock from the transmitter PLL.
Clock Synthesis The maximum input frequency of the PFD of the receiver PLL is 325 MHz. To achieve reference clock frequency above this limit, the Quartus II software enables the divide by 2 pre-divider on the dedicated local REFCLKB path. This divides the reference clock frequency by a factor of 2 and then the /m factor compensates the frequency difference. For example, given a data rate of 2,488 Mbps with a reference clock of 622 MHz, the reference clock must be assigned to the REFCLKB port,
Altera Corporation 2–13 January 2005 Stratix GX Transceiver User Guide Receiver Analog
where the reference clock signal is divided by 2, yielding a 311 MHz clock at the PFD. This 311-MHz reference clock is then multiplied by a factor of 8 to achieve the 2,488-MHz clock at the VCO.
If the reference clock (RX_CRUCLK) exceeds 325 MHz, the clock must be fed by the dedicated local reference clock pin, REFCLKB. By default, the Quartus II software assigns pins to be LVTTL, so a 1.5-V PCML I/O standard assignment is required to select the REFCLKB port as the reference source. The Quartus II software prompts a fitter error if the reference clock exceeds 325 MHz and the reference clock source is not on the REFCLKB port.
The pre-divider on the REFCLKB path is also used to support additional multiplication factors. The block diagram in Figure 2–10 on page 2–13 shows that /m supports only multiplication factors of 8, 10, 16, and 20, but Table 2–4 states that the additional multiplication factors of 2, 4, and 5 can also be achieved.
Without using the transmitter PLL, the pre-divider achieves the multiplication factors of 4 and 5. A multiplication factor of 4 is achieved by pre-dividing the reference clock by 2 and then multiplying the resulting frequency by 8, which yields a multiplication factor of 4. A multiplication factor of 5 is achieved in the same manner by pre-dividing the reference clock by 2 and then multiplying the resulting frequency by 10, which yields a multiplication factor of 5.
The MegaWizard Plug-In altgxb option enables the transmitter PLL in receiver mode. There is also an option to train the receiver CRU with the output of the low-speed transmitter PLL clock. If you select this option, all the multiplication factors that are supported in the transmitter PLL are also supported in the receiver CRU PLL, including the multiplication factor of 2. This option selects the low-speed transmitter PLL clock as the reference source. The low speed transmitter PLL clock is either divided by a SERDES factor of 8 or 10. The receiver PLL then multiplies this reference clock by a factor of 8 or 10 to achieve the same multiplication factor as the transmitter PLL.
For example, a multiplication factor of 2 is achieved on the transmitter PLL by pre-dividing the reference clock by 2 and then multiplying the resultant frequency by 4, which yields a multiplication factor of 2. However, on the low-speed clock output, this frequency is divided by a factor of 8 or 10, depending on the deserialization factor. The low-speed clock feeds the reference of the receiver PLL where the clock is multiplied back up by a factor of 8 or 10, which results in total multiplication factor of 2.
2–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Table 2–5 lists the possible multiplication values as a function of the reference clock source to the receiver PLL. Table 2–5 assumes that the reference clock (RX_CRUCLK) is directly fed from the source listed and does not factor any pre-clock synthesis (that is, a Stratix GX PLL driving a global clock used for the receiver PLL reference clock source).
Table 2–5. Multiplication Values as a Function of the Reference Clock Source to the Receiver PLL
Receiver PLL Reference Clock Source Multiplication Factors Global clock, IO bus, general routing 8, 10, 16, 20 Inter-transceiver routing 4, 5, 8, 10, 16, 20 Dedicated local REFCLKB 4, 5, 8, 10, 16, 20 Low-speed transmitter PLL clock 2, 4, 5, 8, 10, 16, 20 (train CRU with transmitter PLL option)
You specify the data rate of the channel and receiver CRU clock period of the receiver reference clock. The data rate divided by the input clock period must equal one of the multiplication factors listed in Table 2–5.
PPM Frequency Threshold Detector The PPM frequency threshold detector senses whether the incoming reference clock to the CRU and the PLL VCO of the CRU are within a prescribed PPM tolerance range. Valid parameters are 125, 250, 500, or 1,000 PPM. The default parameter, if no assignments are made, is 1,000 PPM. The output of the PPM frequency threshold detector is one of the variables that asserts the rx_freqlocked signal. Refer to “Clock Recovery Unit” on page 2–16 for more detail regarding the rx_freqlocked signal.
Receiver Bandwidth Type The Stratix GX receiver PLL in the CRU offers a programmable bandwidth setting. The bandwidth of a data recovery PLL is the measure of its ability to track the input data and jitter. The bandwidth is determined by the –3-dB frequency of the closed-loop gain of the PLL.
A higher bandwidth setting provides a faster lock time and tracks greater jitter on the input data source, rx_in[], which passes it through the PLL. This helps reject noise from the VCO and power supplies. A low-bandwidth setting, on the other hand, filters out more high-frequency data input jitter, but increases lock time.
Altera Corporation 2–15 January 2005 Stratix GX Transceiver User Guide Receiver Analog
Valid receiver bandwidth settings are low, medium, and high. The –3-dB frequencies for these settings vary due to the non-linear nature and data dependencies of the circuit. You vary the bandwidth to customize the performance on specific systems.
Clock Recovery Unit
The CRU in each Stratix GX receiver channel recovers the clock from the serial data stream on RX_IN. You can set the CRU to automatically or manually alter the receiver PLL phase and frequency to match the bit transition on the incoming data stream. This is to eliminate any clock-to-data skew or to keep the receiver PLL locked to the reference clock (lock-to-data or lock-to-reference mode). The CRU generates two clocks, a high-speed RCVD_CLK to feed the deserializer and a low-speed RCVD_CLK to feed transceiver logic. You can set the CRU to optionally detect run-length violations in the incoming data stream and generate an error whenever the preset run length is exceeded (run-length violation detection circuit).
Lock-to-Reference Mode & Lock-to-Data Mode The Stratix GX device offers both automatic and manual locking options, as described in the following sections.
Automatic Lock Mode By default, the CRU initially locks to the CRU reference clock RX_CRUCLK (lock-to-reference mode) until conditions warrant the switchover to the incoming data (lock-to-data mode). The device switches to the lock-to-data mode when the rx_freqlocked signal goes high. After switching to lock-to-data mode, the CRU requires more time to lock to the incoming serial data.
f For information about the CRU to serial data lock time, which includes frequency lock (during lock-to-reference mode) and phase lock (during lock-to-data mode), refer to the Stratix GX FPGA Family data sheet. Also refer to the Reset Control & Power Down chapter for the recommendations on resets.
To automatically transition from the lock-to-reference mode to the lock-to-data mode, the following conditions must be met:
■ The CRU PLL is within the prescribed PPM frequency threshold setting (125, 250, 500, or 1,000 PPM) of the CRU reference clock. ■ Reference clock and CRU PLL output are phase matched (phases are within 0.08 UI).
2–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
During the lock-to-reference mode, the frequency detector determines whether the reference clock to the receiver PLL and the VCO output are within the prescribed PPM setting.
The phase lock happens when the phase-frequency detector up/down transitions are relatively few and, the pulse widths are sufficiently narrow. These conditions show that the PLL is close to absolute phase lock to the reference clock. This ensures that when actual data signals are sampled, the receiver PLL locks to the fundamental REFCLK frequency and does not drift off to any sub-harmonic.
In lock-to-data mode, the PLL uses a phase detector to keep the recovered clock aligned properly with the data. If the PLL does not stay locked to data because of problems such as frequency drift or severe amplitude attenuation, the receiver PLL locks back to the reference clock of the CRU to train the VCO. When the device is in lock-to-data mode, the CRU tries to align itself with incoming data and there is no phase relationship with the reference clock.
In lock-to-data mode, the rx_freqlocked signal is asserted, and the rx_locked signal looses its significance. The rx_locked signal signifies that the CRU has locked to the reference clock. When the CRU is in lock-to-data mode, the rx_locked signal behavior is not predictable.
In automatic lock mode, CRU is forced out of lock-to-data mode if the CRU PLL is not within the recommended PPM frequency threshold setting (125 PPM, 250 PPM, 500 PPM, 1000 PPM) of the CRU reference clock.
When the CRU goes out of lock-to-data mode, the rx_freqlocked signal goes low. The rx_freqlocked signal also goes low when either the rx_analogreset or pll_areset signal goes high. The rx_analogreset signal powers down the receiver and the pll_areset signal powers down the entire transceiver block (four channels).
Manual Lock Options Two optional input pins, rx_locktorefclk[] and rx_locktodata[], are available that let you control whether the CRU PLL automatically or manually switches between lock-to-reference clock and lock-to-data modes. This lets you bypass the default automatic switchover circuitry if either the rx_locktorefclk[] or rx_locktodata[] signal is instantiated.
When the rx_locktorefclk[] signal is asserted, it forces the CRU PLL to lock to the reference clock (RX_CRUCLK). Asserting the rx_locktodata[] signal forces the CRU PLL to lock to data, whether
Altera Corporation 2–17 January 2005 Stratix GX Transceiver User Guide Receiver Analog
or not the CRU is ready. When both signals are asserted, the rx_locktodata[] signal takes precedence over the rx_locktorefclk[] signal.
You might want to have control over both rx_locktorefclk[] and rx_locktodata[] signals to potentially reduce the CRU lock times. The PPM threshold frequency detector and phase relationship detector require additional latencies to ensure that the CRU is ready to lock to data. These extra latencies are potentially reduced by manually controlling the CRU train signals. You assert the rx_locktorefclk[] signal to initially train the CRU and, after some delta time, assert the rx_locktodata[] signal.
You configure the controller that controls the signals based on your system. You do this by experimenting because many variables must be considered, such as temperature, transition densities, and data rates. However, by doing so, you are not subjected to the CRU lock times required to verify if the two conditions to switch from lock-to-reference mode to lock-to-data mode in the defaulted automatic mode are met. When the rx_locktorefclk goes high, the rx_freqlocked signal is ignored and does not toggle. The rx_freqlocked signal always goes high if lock-to-data mode is asserted. If you want to transition from lock-to-data mode to automatic mode, the transition should be followed by rx_analogreset to send the rx_freqlocked signal low. The CRU does not often transition from manual mode to automatic mode during system operation.
1 The rx_analogreset signal functions like a power down signal as opposed to a digital reset. For more information on various reset signals, refer to the chapter Reset Control & Power Down.
Run Length Violation Detection Circuit The programmable run length violation (RLV) circuit is in the CRU and detects consecutive ones or zeros in the data. If the data stream exceeds the preset maximum number of consecutive ones or zeros, the violation is signified by the assertion of the rx_rlv signal.
The rx_rlv signal is not synchronized to the parallel data, and as a result appears in the logic array earlier than the run-length violation data. To ensure that the FPGA latches this signal in systems where there are frequency variations between the recovered clock and the PLD logic array clock, the rx_rlv signal is asserted for more than two clock cycles in 8- or 10-bit data modes and three clock cycles in 16- or 20-bit data modes.
2–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
If the data width is 8 or 16, set the legal run length threshold values within the range of 4 to 128 UI in multiples of four. If the data width is 10 or 20, or if using 8b10b, set the legal run length threshold values within the range of 5 to 160 UI in multiples of five.
1 See the Stratix GX FPGA Family data sheet to verify the guaranteed maximum run length.
Deserializer (Serial-to-Parallel Converter)
The deserializer converts incoming high-speed serial data streams to either 8- or 10-bit-wide parallel data synchronized to the recovered clock of the CRU. The deserializer drives the parallel data to the pattern detector and word aligner, as shown in Figure 2–11. The data rate of the deserializer output bus is the input data rate divided by the width of the output data bus. For example, for a 10-bit bus and a serial input data rate of 2.5 Gbps, the parallel data rate is 2500/10 or 250 MHz. The first bit into the deserializer is the LSB of the data bus out of the deserializer.
Figure 2–11. Deserializer Block Diagram
Deserializer Serial Data In (From CRU) D7 D7
D6 D6
D5 D5
D4 D4 8 Parallel Data Out (To Word Aligner) D3 D3
D2 D2
D1 D1
D0 D0
High-speed Serial Clock Low-speed Parallel Clock
Figure 2–12 shows the serial bit order of the deserializer input and the parallel data out of the deserializer.
1 The serial data is received LSB to MSB.
Altera Corporation 2–19 January 2005 Stratix GX Transceiver User Guide MegaWizard Analog Features
Figure 2–12. Deserializer Bit Order
Serial clock
Parallel clock
Serial data in 0 11 011 0 0
Parallel data 00 56 out (hex)
MegaWizard This section describes the analog options for the instantiation of the altgxb megafunction in the Quartus II MegaWizard® Plug-In Manager. Analog Features Altera® recommends that the Stratix GX transceiver block be instantiated and parameterized through the MegaWizard Plug-In Manager. The MegaWizard Plug-In Manager offers a graphical user interface (GUI) that organizes the altgxb options in easy-to-use sections. The wizard also sets the proper ports and parameters automatically, based on the options and parameters you select. Invalid settings are automatically flagged to avoid illegal configurations.
Although you can instantiate the Stratix GX block directly by calling out the altgxb megafunction, Altera recommends using the MegaWizard Plug-In Manager to instantiate your altgxb megafunction, reducing the likelihood of invalid settings.
MegaWizard Analog Feature Considerations
Each altgxb MegaWizard Plug-In uses one or more transceiver blocks based on the number of channels you select. There are four channels per transceiver block. If a MegaWizard Plug-In Manager instantiation uses fewer than four channels, the remaining channels in that transceiver block are not available for use.
Each MegaWizard Plug-In Manager instantiation must have similar functionality and data rates. If you want transceiver blocks that differ in functionality and data rates, create a separate MegaWizard Plug-In Manager instantiation for each transceiver block.
As mentioned in the clocking section, the MegaWizard Plug-In Manager also displays the configuration of the altgxb megafunction. Figures 2–13 through 2–19 change dynamically based on the selected mode, options, and clocking schemes.
2–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Figure 2–13. MegaWizard Plug-In Manager - ALTGXB (Page 1 of 7) - General (1) Notes (1)–(4)
Notes to Figure 2–13: (1) Option available in receiver-only mode: Supports use of the transmitter PLL even when the transmit channel is disabled. Provides a non-recovered clock output for the logic array. (2) Enables the transmitter PLL to train the receiver PLL: Use this option to support additional multiplication factors for the receiver PLL. This option also supports the separation of receiver and transmitter reference clocks. An additional input receiver reference clock (rx_cruclk) is available when this option is turned off. The first option that is enabled is needed for non-encoded 16-bit modes with a line rate of 2,600 Mbps or greater. For more details regarding this feature, refer to “Clock Synthesis” on page 2–6. (3) Selectable High and Low: High bandwidth supports faster lock times. It also tracks higher frequency jitter (based on the –3-db frequency of the PLL gain plot) on the input clock. Low bandwidth has a smaller pass band to filter out more high-frequency jitter, but has a slower lock time. (4) Selectable PPM difference tolerance {125, 250, 500, 1000} between the Receiver PLL VCO and the CRU clock: This is one of three parameters that affect the rx_freqlocked signal. If an out-of-tolerance event occurs, rx_freqlocked goes low.
Altera Corporation 2–21 January 2005 Stratix GX Transceiver User Guide MegaWizard Analog Features
Figure 2–14. MegaWizard Plug-In Manager - ALTGXB (Page 2 of 7) - General (2) Notes (1), (2)
Notes to Figure 2–14: (1) For information, refer to the Loopback Modes chapter. (2) For more information, refer to the Stratix GX Built-In Self Test (BIST) chapter.
2–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Figure 2–15. MegaWizard Plug-In Manager - ALTGXB (Page 3 of 7) - Receiver (1) Note (1)
Note to Figure 2–15: (1) Enable run length violation circuit. If enabled, the optional output pin rx_rlv pin is available and pulses high when the specified run length is violated. In 8-bit or 16-bit mode, set the run length threshold from 4 to 124 in steps of 4. In 10-bit and 20-bit mode, or if using 8b10b, set the run length threshold from 5 to 160 in steps of 5.
Altera Corporation 2–23 January 2005 Stratix GX Transceiver User Guide MegaWizard Analog Features
Figure 2–16. MegaWizard Plug-In Manager - ALTGXB (Page 4 of 7) - Receiver (2) Notes (1)–(3)
Notes to Figure 2–16: (1) Stratix GX to Stratix GX DC coupling only. Lets the receiver accept a 1.5-V PCML signal from a Stratix GX transmitter buffer. (2) The Use equalizer control signal option enables dynamic equalization via the optional rx_equalizerctrl input port. If this control signal is not used, you can set equalization in the MegaWizard Plug-In Manager via the Select the equalizer control setting. The valid values are 0 through 4, with 0 being off and 4 being the largest gain setting. (3) Available settings are High, Medium, and Low. High bandwidth allows for faster lock times and tracks higher frequency jitter (based on the -3 db frequency of the PLL gain plot) on the input clock. Low bandwidth contains a smaller pass band to filter out more high-frequency jitter, but has slower lock times.
2–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Figure 2–17. MegaWizard Plug-In Manager - ALTGXB (Page 5 of 7) - Receiver (3) Notes (1)–(3)
Notes to Figure 2–17: (1) Optional input signal that forces the CRU to lock to the reference clock. This disables the auto switch- over mode that switches the CRU to lock-to-data mode. If both rx_locktorefclk and rx_locktodata are asserted, then rx_locktodata takes precedence. (2) Optional input signal that forces the CRU to lock to the incoming data. If both rx_locktorefclk and rx_locktodata are asserted, rx_locktodata takes precedence. (3) Optional output signal that indicates when the CRU is locked to the incoming data stream. The lock indication is based on the following conditions: a. The CRU PLL is within the prescribed PPM frequency threshold setting (125 PPM, 250 PPM, 500 PPM, 1,000 PPM) of the CRU reference clock. b. The reference clock and CRU PLL output are phase matched (~ phases are within 0.08 UI).
Altera Corporation 2–25 January 2005 Stratix GX Transceiver User Guide MegaWizard Analog Features
Figure 2–18. MegaWizard Plug-In Manager - ALTGXB (Page 6 of 7) - Transmitter Notes (1), (2)
Notes to Figure 2–18: (1) The Use VOD control signal option enables dynamic VOD adjustment via the optional tx_vodctrl input port. If this control signal is not used, set the VOD in the MegaWizard Plug-In Manager via the Select the VOD control setting option. The valid values are based on your transmitter termination value and range from 400 to 1,600 mV. (2) The Use Preemphasis control signal option enables dynamic pre-emphasis control using the optional tx_preemphasisctrl input port. If this control signal is not used, set the pre-emphasis in the MegaWizard Plug-In Manager using the Select the preemphasis control setting. The valid values are 1 through 5, where 1 is the smallest pre-emphasis value and 5 is the largest. The amount of pre-emphasis is based on your VOD values.
2–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Analog Description
Figure 2–19. MegaWizard Plug-In Manager - ALTGXB (Page 7of 7) - Summary
Altera Corporation 2–27 January 2005 Stratix GX Transceiver User Guide MegaWizard Analog Features
2–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 3. Basic Mode
Introduction The basic mode of the Stratix® GX device includes the following features:
■ Serial data rate range from 500 Mbps to 3.1875 Gbps ■ Input reference clock range from 25 to 650 MHz ■ Parallel interface width of 8, 10, 16, or 20-bit support ■ 8B/10B encoder/decoder can be enabled or bypassed ■ Word aligner supports 7-bit, 10-bit, 16-bit, or bit slip mode
Applications like packet or streaming data applications, chip-to-chip connectivity, backplanes, or board-to-board connectivity, which do not have a defined protocol overhead or a custom protocol to transfer data serially over a medium, can use the basic mode offered by Stratix GX devices. The basic mode includes SERDES and parallel interconnect functionality. In this mode, the transceiver performs serialization and de- serialization with an optional 8B/10B coding scheme. Basic mode is not aware of the system level protocol wrapped on top of it.
Basic mode enables a subset of the transceiver blocks for customizable configuration. The channel aligner and the rate matcher features are not available in basic mode.
This chapter details the supported digital architecture, clocking schemes, and software implementation for basic mode. Figure 3–1 shows a block diagram of a duplex channel configured in basic mode.
The digital section starts at the word aligner of the receiver channel and propagates up to the device logic array.
Altera Corporation 3–1 January 2005 Basic Mode Receiver Architecture
Figure 3–1. Block Diagram of a Duplex Channel Configured in Basic Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
Basic Mode Figure 3–2 shows a block diagram of the digital components of the Receiver receiver in basic mode. Architecture
Figure 3–2. Block Diagram of the Receiver Digital Components in Basic Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Receiver
Word Aligner
For embedded clocking schemes, the clock is recovered from the incoming data stream based on transition density of the data. This feature eliminates the need to factor in receiver skew margins between the clock and data. However, with this clocking methodology, the word boundary of the re-timed data can be altered. Stratix GX devices offer an embedded
3–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
word alignment circuit that is used in conjunction with the pattern detector to align the word boundary of the re-timed data to a specified comma. In basic mode, this embedded circuit is configured to manual alignment mode, which consists of 10-bit, 16-bit, and bit-slip modes.
The word aligner is composed of a pattern detector, manual alignment controller, bit-slipper circuitry, and synchronization state machines. Depending on the configuration, these components work in conjunction or independently of one another. The word aligner cannot be bypassed, but if the rx_enacdet signal is not used, the word aligner does not alter the data. Figure 3–3 shows the various components of the word aligner in basic mode. The functionality is described in the following sections.
Figure 3–3. Components in the Stratix GX Word Aligner
Word Aligner
Manual Pattern Alignment Mode Detector
Bit-Slip 10-Bit Mode Mode 10-Bit 16-Bit 7-Bit Mode Mode Mode
16-Bit Mode A1A2 Mode
Pattern Detector Module The pattern detector matches a predefined comma to the current byte boundary. If the comma is found, the optional rx_patterndetect signal is asserted for the duration of one clock cycle to signify that the comma exists in the current word boundary. The pattern detector module only indicates that the signal exists and does not modify the word boundary. Modification of the word boundary is discussed in the word alignment and synchronization sections.
Altera Corporation 3–3 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
A 10-bit pattern, 7-bit pattern, or 16-bit pattern can be programmed for the pattern detector to recognize. Refer to the section “Basic Mode MegaWizard Plug-In” on page 3–29 for more details.
10-Bit Pattern Mode When the word alignment pattern length parameter in the MegaWizard® Plug-In Manager is set to 10, the module matches the 10-bit comma with the data and its complement in the current word boundary. Both positive and negative disparities are checked in this mode. For example, if a /K28.5/ (b'0011111010) pattern is specified as the comma, the rx_patterndetect is asserted if b'0011111010 or b'1100000101 is detected in the incoming data.
7-Bit Pattern Mode When the word alignment pattern length parameter in the MegaWizard Plug-In Manager is set to 7, the module matches the 7-bit comma specified in the wizard field parameter with the seven least significant bits (LSB) of the data and its complement in the current word boundary. Both positive and negative disparities are also checked in this mode.
The 7-bit pattern mode is useful because it can mask out the three most significant bits of the data. This lets the pattern detector recognize multiple commas. For example, in the 8b/10b encoded data, a /K28.5/ (b'0011111010), /K28.1/ (b'0011111001), and /K28.7/ (b'0011111000) shares seven common LSBs, so masking the three MSBs lets the pattern detector resolve all three commas.
16-Bit Pattern Mode The two consecutive 8-bit characters (A1A2) are used as the comma in 16-bit pattern mode.
A1 represents the least significant byte, which consists of bits [7..0], and A2 represents the most significant byte, consisting of bits [15..8]. Therefore, the comma must be specified as [A2,A1] in the MegaWizard Plug-In Manager word alignment comma section. Only the positive disparity of the comma is detected in the mode. The A1A1A2A2 mode is only available when SONET is specified as the protocol.
Table 3–1. Pattern Detector Comma Patterns in Basic Mode
Pattern Detect Mode Data Width Disparity 10-bit 10-bits, 20-bits ± 7-bit 10-bits, 20-bits± Two consecutive 8-bit characters 8-bits, 16-bits +
3–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Manual Alignment Modes The Stratix GX device supports manual alignment in 10-bit, 16-bit, and bit-slipping modes.
Manual 10-Bit Alignment Mode You can configure the word aligner to align to a 10-bit word boundary if you use 8B/10B encoding or if you specify the data width to be either 10- or 20-bits wide. In this mode, the internal word alignment circuitry barrel shifts the correct word boundary if the comma specified in the pattern detector is detected in the data stream.
When rx_enacdet[] is high, the word aligner detects the specified comma and re-aligns the byte boundary, if needed. The rx_syncstatus[] signal is asserted for one clock cycle to signify that the word boundary has been synchronized. The rx_enacdet[] signal can be held high if the comma is known to be unique and does not also appear across the byte boundaries of other data. For example, if the design uses an encoding scheme such as 8B/10B to guarantee that the /K28.5/ code group is a unique pattern in the data stream, the rx_enacdet is held high. In situations where the comma exists between word boundaries, rx_enacdet must be controlled to avoid false word alignment. For example, suppose that you use 8B/10B encoding and specify a /+D19.1/ (b'110010 1001) character as the comma. In this case, a false word boundary is detected if a /-D15.1/ (b'010111 1001) is followed by a /+D18.1/ (b'010011 1001). (See Figure 3–4.)
Figure 3–4. False Word Boundary Alignment if the Comma Exists Across Word Boundaries
-D15.1 +D18.1 ….... ….... 01011110010100111 0 01
+D19.1
The rx_enacdet signal must be deasserted after the initial word alignment is found, so as to prevent false word boundary alignment. When rx_enacdet is deasserted, the current word boundary is locked even if the comma is detected across different boundaries. In this case, rx_syncstatus[] acts as a re-synchronization signal to signify that the comma was detected, but the boundary is different than the current boundary. For best results, monitor this signal and reassert rx_enacdet[], if re-alignment is desired.
Altera Corporation 3–5 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
Figure 3–5 shows an example of how the word aligner signals interact in 10-bit alignment mode. For this example, a /K28.5/ (10'b0011111010) is specified as the comma. Because rx_enacdet is held high at time n, alignment occurs whenever a comma exists in the pattern. The rx_patterndetect signal is asserted for one clock cycle to signify that the pattern exists on the re-aligned boundary. The rx_syncstatus signal is also asserted for one clock cycle to signify that the boundary has been synchronized.
Figure 3–5. Example of How the Word Aligner Symbols Interact in 10-Bit Manual Alignment Mode
n n+1 n+2 n+3 n+4 n+5
rx_recovclockout
rx_word_align_out 111110000 0101111100 1111100001111001010 1000000101 111110000 0101111100
rx_enacdet
rx_patterndetect
rx_syncstatus
At time n+1 the rx_enacdet signal is deasserted, which instructs the word aligner to lock the current word boundary. The comma is detected at time n+2, but it exists on a different boundary than the current locked boundary. Because the bit orientation of the Stratix GX device is LSB to MSB, it follows, from the waveform, that the comma exists across time n+2 and n+3. In this condition, the rx_patterndetect signal remains low because the comma does not exist on the current word boundary, but the rx_syncstatus signal is asserted for one clock cycle to signify a resynchronization condition. This means that the comma has been detected, but across another word boundary. The logic of the design determines whether to assert the rx_enacdet signal to re-initiate the word alignment process. At time n+5 the rx_patterndetect signal is asserted for one clock cycle to signify that the comma has been detected on the current word boundary.
Manual 16-bit Alignment Mode You can enable the 16-bit alignment mode if the data widths are 8-bits or 16-bits. This mode is similar to the manual A1A2 SONET alignment mode, except that the rx_a1a2size[] and rx_a1a2sizeout[] signals are not available.
3–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
The byte boundary is locked after the first comma is detected and aligned after the rising edge of the rx_enacdet[] signal. If the byte boundary changes, the rx_enacdet[] signal must be deasserted and reasserted to reset the alignment circuit. On the rising edge of the rx_enacdet[], the word aligner locks onto the first comma detected. In this scenario, the rx_patterndetect[] signal is asserted to signify that the comma has been aligned. Also, the rx_syncstatus[] signal is asserted for a clock cycle to signify that the word boundary has been synchronized. After the word boundary has been locked, regardless of whether the rx_enacdet[] is high or low, the rx_syncstatus[] signal asserts itself for one clock cycle whenever a comma is detected across a different byte boundary. The rx_syncstatus[] signal operates in this re- synchronization state until a rising edge is detected on rx_enacdet[].
Figure 3–6 shows how the word aligner signals interact in 16-bit alignment mode for an A1A2 pattern.
Figure 3–6. Example of How the Word Aligner Signals Interact in SONET A1A2 Manual Alignment Mode
n n+1 n+2 n+3 n+4 n+5 n+6
rx_recovclockout
rx_word_align_out 01101111 00010100 11111000001000110 00000001 01101111 00010100
rx_enacdet
rx_patterndetect
rx_syncstatus
In Figure 3–6, the rx_enacdet signal is toggled high at time n, at which point the aligner locks to the boundary of the next present comma. The A1 comma also appears on the rx_word_align_out port during this period. At time n+1 the A2 comma appears on the rx_word_align_out port. Because the comma exists, the rx_patterndetect and rx_syncstatus signals are asserted for one clock cycle to signify that the A1A2 comma has been detected and the word boundary has been locked. The A1A2 comma appears again across word boundaries during periods n+2, n+3, and n+4. The rx_enacdet signal is held high, but the word aligner does not re-align the byte boundary as it would in 10-bit manual alignment mode. Instead, the rx_syncstatus signal is asserted for one clock cycle to signify a re-synchronization condition. You must deassert and reassert the rx_enacdet signal to retrigger the word aligner. The next transition occurs at time n+5, where rx_enacdet is
Altera Corporation 3–7 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
deasserted and the A1 pattern is present on the rx_word_align_out port. At time n+6, the A2 pattern is present on the rx_word_align_out port. The word aligner then asserts the rx_patterndetect signal for one clock cycle to flag the detection of the comma on the current word boundary.
Manual Bit-Slipping Alignment Mode You can also achieve word alignment by enabling the manual bit-slip option. With this option enabled, the transceiver has the ability to shift the word boundary one-bit every parallel clock cycle. Bits are shifted from the MSB to LSB direction. Shifting occurs every time the bit-slipping circuitry detects a rising edge of the rx_bitslip[] signal. Each time a bit is slipped, the bit that arrived at the receiver earlier is skipped. When the word boundary matches what is specified as the comma, the rx_patterndetect[] signal is asserted for one clock cycle. For best results, implement the logic in the device logic array to control the bit-slip circuitry.
This scheme is useful if the comma changes dynamically when the Stratix GX device is in user mode. Because the controller is implemented in the logic array, a custom controller can be built to dynamically change the comma without needing to reprogram the Stratix GX device.
Figure 3–7 shows an example of how the word aligner signals interact in the manual bitslip alignment mode. For this example, 8'b00111100 is specified as the comma, and an 8'b11110000 value is held at the rx_in port. Every rising edge on the rx_bitslip port causes the rx_word_align_out data to shift a bit from the MSB to the LSB. This shifting is shown at time n+2, where the 8'b11110000 data is shifted to a value of 8'b01111000. At this state, the rx_patterndetect is held low, because the specified comma does not exist in the current word boundary. The rx_bitslip is disabled at time n+3 and re-enabled at time n+4. The output of the rx_word_align_out now matches the specified comma, so the rx_patterndetect is asserted for one clock cycle. At time n+5 the rx_patterndetect is still asserted since the comma still exists in the current word boundary. Finally, at time n+6 the rx_word_align_out boundary is shifted again, and the rx_patterndetect signal is deasserted to signify that the word boundary does not contain the comma.
3–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–7. Example of How the Word Aligner Symbols Interact in Manual Bitslip Mode
n n+1 n+2 n+3 n+4 n+5 n+6
rx_recovclockout
rx_in 11110000
rx_word_align_out 11110000 01111000 00111100 00011110
rx_bitslip
rx_patterndetect
Table 3–2. Word Alignment Support for Basic Mode
Control Word Alignment Mode Effective Mode Status Signals Signals Manual 10-bit alignment Alignment to detected pattern when rx_enacdet rx_syncstatus Mode allowed by the rx_enacdet signal rx_patterndetect Manual 16-bit alignment Alignment to detected pattern when rx_enacdet rx_syncstatus Mode allowed by the rx_enacdet signal rx_patterndetect Manual bit-slipping Manual bit slip controlled by the device rx_bitslip rx_patterndetect alignment mode logic array
8B/10B Decoder
The 8B/10B decoder is part of the Stratix GX transceiver block. The 8B/10B decoder restores the 8-bit data + 1-bit control identifier from the 10-bit code.
10-bit Decoding The 8B/10B decoder translates the 10-bit encoded code into the 8-bit equivalent data or control code. The 10-bit encoded code is received LSB to MSB. The data received must come from the supported Dx.y or Kx.y list. All 8B/10B control signals (Disparity error, control detect, and code error) are pipelined with the data in the Stratix GX receiver block and are edge-aligned with the data. Figure 3–8 diagrams the 10-bit to 8-bit conversion.
Altera Corporation 3–9 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
Figure 3–8. 10-Bit to 8-Bit Conversion
jhg fiedcba
9 8 7 6 5 4 3 2 1 0
MSB received LSB received last first
8b-10b conversion
7 6 5 4 3 2 1 0 Parallel Data + CTRL
HGFEDCBA
Reset The rxdigitalreset signal governs the reset condition of the 8B/10B decoder. In reset, the disparity registers are cleared. Upon exiting reset, the 8B/10B decoder can start with either a positive or negative disparity. The decoder calculates the initial running disparity based on the first valid code received.
The receiver block must be word aligned after reset before the 8B/10B decoder can decode valid data or control codes.
Code Error Detect The rx_errdetect signal indicates when the code that is received contains an error. This port is optional and if not in use, there is no way to determine whether a code that is received is valid. The rx_errdetect signal goes high if a code received is an invalid code or if it contains a disparity error. If a code is received that is not part of the valid Dx.y or Kx.y list, the rx_errdetect signal goes high. This signal is aligned with the invalid code word that is received at the device logic array and/or the code word that triggered the disparity error.
3–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Disparity Error Detector The 8B/10B decoder can detect disparity errors based on which 10-bit code it received. The disparity error is indicated at the optional rx_disperr port. The current running disparity is based on the disparity calculation of the last code it received. The disparity calculation is described in Appendix A, Data & Control Codes.
If negative disparity is calculated for the last 10-bit code, a neutral or positive disparity 10-bit code is expected. If the decoder does not receive a neutral or positive disparity 10-bit code as the next code word, the rx_disperr signal goes high, indicating that the code that was received contained a disparity error.
If a positive disparity is calculated, the next code-group must be a neutral or negative disparity 10-bit code. The rx_disperr signal goes high if the code that is received is not as expected. When the rx_disperr signal transitions high, rx_errdetect also transitions high.
Figure 3–9 shows a case where the disparity is violated. A K28.5 code has an 8-bit value of 8'hbc and a 10-bit value (jhgfiedcba). The 10-bit value is 10'b0011111010 (10'h17c) for RD- or 10'b1100000101 (10'h283) for RD+. Assume that the running disparity at time n-1 is negative, so the expected code at time n is taken from the RD- column. Because a K28.5 does not have a balanced 10-bit code (equal number of 1’s and 0’s), the expected RD code toggles back and forth between RD- and RD+. At time n+3, the 8B/10B decoder received a RD+ K28.5 code (10'h283), which would make the current running disparity negative. At time n+4, because the current disparity is negative, a K28.5 from the RD- column is expected, but a K28.5 code from the RD+ is received instead. This code prompts rx_disperr to go high during time n+4 to indicate that this particular K28.5 code contained a disparity error. The current running disparity at the end of time n+4 is negative because a K28.5 from the RD+ column was received. Based on the current running disparity at the end of time n+5, a positive disparity K28.5 code (from the RD-) column is expected at time n+5.
Altera Corporation 3–11 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
Figure 3–9. Disparity Error
n n+1 n+2 n+3 n+4 n+5 n+6 n+7
clock
rx_out[7:0 ] BC BC BC BCxx BC BC BC
rx_disperr
rx_errdetect
rx_ctrldetect
Expected RD code RD- RD+RD- RD+ RD- RD- RD+ RD-
RD code received RD- RD+RD- RD+ RD+ RD- RD+ RD-
rx_in 17C 283 17C 283 28317C 283 17C
Control Detect The 8B/10B can differentiate between data and control codes via the rx_ctrldetect port. This port is optional, and if it is not in use, there is no way of differentiating a Dx.y from a Kx.y.
Figure 3–10 shows an example waveform demonstrating the receipt of a K28.5 code (BC + ctrl). The rx_ctrldetect=1'b1 is aligned with 8'hbc, indicating that it is a control code.
Figure 3–10. Control Code Detection
clock
rx_out[7:0] 83 78 BC BC 0F 00 BF 3C
rx_ctrldetect
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
3–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Byte Deserializer
The byte deserializer module further reduces the speed at which the FPGA logic array must run in order to meet performance. If the input is 10 bits of data, the output to the FPGA logic array is deserialized to 20 bits. If the input is 8 bits of data, the output to the FPGA logic array is deserialized to 16 bits. The byte deserializer does not process the data and as such, the control signals that are fed to the module are only processed to match the latency to the data.
The byte deserializer in the receiver block takes in a maximum of 13 bits. It is possible to feed the following to the byte deserializer:
■ 8 bits of data and up to three control signals (rx_patterndetect, rx_syncstatus, and rx_a1a2sizeout) ■ 8 bits of data and up to five control signals (rx_patterndetect, rx_syncstatus, rx_disperr, rx_ctrldetect, and rx_errdetect) ■ 10 bits of data and up to two control signals (rx_patterndetect and rx_syncstatus)
The byte deserializer outputs up to 26 bits, depending on the number of bits that was passed to it. When the input includes data and control signals, the data and the control signals are deserialized to include double the data bits and two bits of each control signal, one for the MSB and one for the LSB. The aggregate bandwidth does not change by using the byte deserializer, because the logic array data width is doubled.
Figure 3–11 demonstrates input and output signals of the byte deserializer when deserializing a 10-bit data input to 20 bits. In this case, the alignment pattern A (1010100000) is located in the MSB of the 20-bit output, and this is reflected with patterndetect [1] going high. The output of the byte deserializer is AX, CB, ED, and so on.
Altera Corporation 3–13 January 2005 Stratix GX Transceiver User Guide Basic Mode Receiver Architecture
Figure 3–11. Receiver Byte Deserialzer in 10/20-Bit Mode With Alignment Pattern in MSB
inclk X ABCDE
xxxxxxxxxx 1010100000 1100011000 1111000111 1010101010 1100110011 data_in[9..0] AX CB
xxxxxxxxxxxxxxxxxxxx 1010100000xxxxxxxxxx 11110001111100011000 data_out[19..0]
patterndetect[0]
patterndetect[1]
Figure 3–12 demonstrates the alternate case of the alignment pattern found in the LSB of the 20-bit output. Correspondingly, patterndetect[0] goes high. In this case, the output is BA, DC, FE, and so on.
Figure 3–12. Receiver Byte Deserialzer in 10/20-Bit Mode With Alignment Pattern in LSB
inclk
A B C D E F
data_in[9..0] 1010100000 1100011000 1111000111 1010101010 1100110011 1111100000
BA DC
data_out[19..0] xxxxxxxxxxxxxxxxxxxx 11000110001010100000 10101010101111000111
patterndetect[0]
patterndetect[1]
You must implement logic for byte position alignment, if necessary, once data enters the logic array, as seen in Figure 3–13. In this example, the byte position selection logic determines the proper byte position based on the pattern detect signal.
3–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–13. Receiver Byte Deserialzer Data Recovery in Logic Array
Gigabit Transceiver Block Logic Array
rx_out[19..10] rx_out_post[19..10] DQ 10 10 rx_out_post[19..0] 10 rx_out_align[19..0] Phase 10 Compensation 20 FIFO Buffer {rx_out[9..0], rx_out_post[19..10]}
rx_out[9..0] rx_out_post[9..0] DQ 10 10
Byte Boundary Selection Logic
Receiver Phase Compensation FIFO Buffer
The receiver phase compensation FIFO buffer is located at the FPGA logic array interface in the receiver block and is four words deep. The buffer compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
In basic mode, the write port is clocked by the recovered clock from the CRU. This clock is half the original rate if the byte deserializer is used. The read clock is clocked by RX_CORECLK.
You can select RX_CORECLK as an optional receiver input port, and it can also accept a clock supply. The clock that feeds the RX_CORECLK must be derived from the RX_CLKOUT of its associated receiver channel. The receiver phase compensation FIFO buffer can only account for phase differences.
Altera Corporation 3–15 January 2005 Stratix GX Transceiver User Guide Basic Mode Transmitter Architecture
In basic mode, if the RX_CLKOUT port is not selected for use, the read clock is clocked by RX_CORECLK, which is fed by RX_CLKOUT. An FPGA global clock, regional clock, or fast regional clock resource is required to make the connection for the read clock. Refer to the section “Basic Mode Channel Clocking” on page 3–20 or the block diagram in the MegaWizard Plug-In Manager for more information on the clock structure in a particular mode.
The receiver phase compensation FIFO buffer is always used and cannot be bypassed.
Basic Mode Figure 3–14 shows the components of the transmitter block that are used Transmitter in the basic mode of operation. Architecture
Figure 3–14. Block diagram of the Transmitter Digital Components in Basic Mode
Analog Section Digital Section
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Transmitter
Transmitter Phase Compensation FIFO Buffer
The transmitter phase compensation FIFO buffer is located at the FPGA logic array interface in the transmitter block and is four words deep. The phase compensation FIFO buffer compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
The read port of the phase compensation FIFO module is clocked by the transmitter PLL clock. The write clock is clocked by TX_CORECLK. You can select the TX_CORECLK as an optional transmitter input port in which to supply a clock. In this case, you must ensure that there is no frequency difference between the TX_CORECLK and the Transmitter PLL clock. The transmitter phase compensation FIFO buffer can only account for phase differences.
3–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
If the TX_CORECLK is not selected as an optional input transmitter port, TX_CORECLK is fed by CORECLK_OUT. This connection occurs using the logic array routing. In this situation, the software defaults to using an FPGA global clock, a regional clock, or a fast regional clock resource.
The transmitter phase compensation FIFO buffer is always used and cannot be bypassed. The input to the transmitter phase compensation FIFO module is the data from the device logic array. If they are used, the tx_ctrlenable and tx_forcedisparity signals are also passed through the FIFO module to ensure that they are synchronized with the data when they feed the 8B/10B encoder module.
Byte Serializer
The byte serializer in the transmitter block takes in a 20- or 16-bit input from the phase compensation FIFO module and serializes it to 10 or 8 bits. It transmits the least significant byte to the most significant byte. Altera® recommends using the transmitter digital reset to reset the byte serializer FIFO module pointers whenever an unknown state is encountered: for example, periods when the transmitter PLL unlocks. Refer to the Reset Control & Power Down chapter for further details on the reset sequence.
Figure 3–15 demonstrates input and output signals of the byte serializer when serializing a 20-bit input to 10 bits. The tx_in[] signal is the input from the FPGA logic array that has already passed through the transmitter phase compensation FIFO buffer.
Figure 3–15. Transmitter Byte Serializer in 20- to 10-Bit Mode
D1 D2 D3
datain[19..0] 11111000001010100000 11000110001111000111 10101010101100110011
dataout[9..0] xxxxxxxxxx xxxxxxxxxx 1010100000 1111100000 1111000111 1100011000 LSB MSB LSB MSB
D1 D2
The LSB is transmitted before the MSB in the Transmitter byte serializer. For the input of D1, the output is D1LSB and then D1MSB.
8B/10B Encoder
The 8B/10B encoder is part of the Stratix GX transceiver block. The purpose of the 8B/10B encoder is to translate 8-bit data and a 1-bit control identifier (via tx_ctrlenable) into a 10-bit DC-balanced data stream.
Altera Corporation 3–17 January 2005 Stratix GX Transceiver User Guide Basic Mode Transmitter Architecture
For additional information regarding the 8B/10B code itself, refer to Appendix A, Data & Control Codes. The 8B/10B encoder translates the 8- bit data or 8-bit control character to its 10-bit equivalent. The conversion format is shown in Figure 3–16. The 10-bit resultant data is transmitted LSB first by the serializer.
Figure 3–16. 8B/10B Conversion Format
7 6 5 4 3 2 1 0 + CTRL
HGFEDCBA
8b-10b conversion
jhg fiedcba
9 8 7 6 5 4 3 2 1 0
MSB sent last LSB sent first
8B/10B Reset Condition The txdigitalreset controls the reset of the 8B/10B encoder. To reset the 8B/10B encoder, txdigitalreset must be high. During reset, the running disparity registers are cleared, as are the data registers. Also, the 8B/10B encoder outputs a K28.5 pattern from the RD- column continuously until txdigitalreset is low. The tx_in[] and tx_ctrlenable[] are ignored during the reset state. Once out of reset, the 8B/10B encoder starts with a bias towards negative disparity (RD-) and transmits three K28.5 code for synchronizing before it starts encoding and transmitting the data on tx_in[].
If the reset for the 8B/10B encoder is asserted, the 8B/10B decoder receiving the data might receive an invalid code error, sync error, control detect, and/or disparity error while txdigitalreset is high.
3–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–17 shows the reset behavior of the 8B/10B encoder. When in reset (txdigitalreset is high), a K28.5- (K28.5 10-bit code from the RD- column) is sent continuously until txdigitalreset is low. Because of the pipelining of the transmitter channel, there are some don't-care values (10'hxxx) until the first of three K28.5 is sent (Figure 3–17 shows three don't-cares). Normal user data follows the third K28.5.
Figure 3–17. Transmitter Output During Reset Conditions
clock
txdigitalreset
tx_out[9:0 ] K28.5- K28.5- K28.5- xxx xxx xxx K28.5- k28.5+ K28.5- Dx.y+
Control Code Encoding The tx_ctrlenable[] controls when a control code is to be inserted in the encoded data flow. When tx_ctrlenable[] is low, the byte at tx_in[] is encoded as data. When tx_ctrlenable[] is high, tx_in[] is encoded as a control word. Figure 3–18 shows that the second 0xBC is encoded as a control code. The others are encoded as data.
Figure 3–18. Control Word Identification Waveform
clock
tx_in[7:0] 83 78 BC BC 0F 00 BF 3C
tx_ctrlenable
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
The 8B/10B encoder does not check whether the control code word entered is one of the 12 valid control code-groups. If an invalid control code is entered, the resulting 10-bit code might also be invalid (might not map to a valid Dx.y or Kx.y code), depending on the value entered.
Altera Corporation 3–19 January 2005 Stratix GX Transceiver User Guide Basic Mode Clocking
An example would be the invalid code encoding of a K24.1 (data = 8'h38 + tx_ctrlenable = 1'b1). Depending on the current running disparity, the K24.1 can be encoded to be 10'b0110001100 (0x18C), which is equivalent to a D24.6+ (0xD8 from the RD+ column). An 8B/10B decoder would decode this value incorrectly.
Basic Mode Two types of clocking are available in basic mode: channel clocking and Clocking inter-transceiver clocking. Basic Mode Channel Clocking
This section describes internal clocking and the external clocks of the transceiver in basic mode. By default, the MegaWizard Plug-In Manager parameterizes the altgxb megafunction with the clock configuration shown in Figure 3–19.
Figure 3–19. Default Configuration of the altgxb Megafunction in Basic Mode
The altgxb megafunction (shown in basic mode in Figure 3–19) is configured such that the train receiver PLL with transmitter PLL is enabled. The transmitter PLL is fed from an inclk port, which itself can be fed from a dedicated REFCLKB, global clock, regional clock, or fast regional clock source. The receiver logic is clocked by the recovered clock from the CRU, which is rx_clkout. This recovered clock is also fed into the device so that in a multi-crystal environment, some level of clock domain decoupling can be implemented to interface with a system clock.
3–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
On the transmitter channel the output of the transmitter PLL, coreclk_out, is sent into the logic array and also loops back to clock the write side of the transmit phase compensation FIFO buffer.
You can disable the trained receiver PLL CRU clock from the transmitter PLL feature in the MegaWizard Plug-In Manager. Deselecting this option adds an additional RX_CRUCLK input reference clock port for the receiver PLL. This feature supports additional multiplication factors for the receiver PLL and also supports the separation of receiver and transmitter reference clocks. This separation is required if the output reference clock frequency from the transmitter PLL exceeds the 325-MHz phase frequency detector of the receiver PLL. For more information on this feature, refer to the Stratix GX Analog Description chapter. This configuration is shown in Figure 3–20.
If double width is used (16-bit bus) and the data rate is above 2,600 Mbps, the train receiver PLL clock from the transmitter PLL must be turned off, because the output clock from the transmitter PLL exceeds the 325-MHz limit on the receiver PLL input clock, if the input clock is fed by any non-REFCLKB pins. REFCLKB input pins have a 650-MHz limit.
Figure 3–20. altgxb Megafunction in Basic Mode With the Train Receiver CRU From Transmitter PLL Disabled
Altera Corporation 3–21 January 2005 Stratix GX Transceiver User Guide Basic Mode Clocking
This configuration has an independent rx_cruclk that feeds the receiver PLL reference clock. This input clock port is only available when the receiver PLL is not trained by the transmitter PLL. There is one rx_cruclk associated with a channel. If four channels are active, there are four rx_cruclk signals.
The RX_CLKOUT is the recovered clock from the associated receiver channel. One rx_clkout is available for each receiver channel that is used. You can use this clock to clock the rate-matching FIFO buffer write port in the device. The read port of the FIFO buffer can be clocked by the CORECLK_OUT signal or device clock.
The CORECLK_OUT port is the output from the transmitter PLL. A CORECLK_OUT port is available for each transceiver block used. You should use the CORECLK_OUT clock to clock the transmitter input.
The receiver phase compensation FIFO buffer read clock and the transmitter phase compensation FIFO buffer write clock can be optionally enabled to manually feed in a clock from the device buffer write block. You can use these options to optimize the global clock usage. For example, if all transmitter channels between transceiver blocks are from a common clock domain, the transceiver instantiations use only one global resource clock instead of one global per transceiver block, if the TX_CORECLK option is disabled.
The situation is similar for the receiver channels in a single-crystal synchronous system with RX_CORECLK. During initialization or long run lengths, the recovered clock becomes asynchronous with the system clock. As a result, the pointers of the receiver phase compensation FIFO buffer might overlap and fail to function correctly. In these situations, the receiver phase compensation FIFO buffers must be reset by the rxdigitalreset signal.
In multi-crystal environments, individual recovered clocks must drive the read clock of the phase compensation FIFO buffer. The Quartus® II software does so by default and you do not need to manually make this connection. The rx_coreclk and tx_coreclk must be frequency matched with their respective read and write ports. Figure 3–21 shows the clock configuration with these optional input ports enabled.
3–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–21. altgxb in Basic Mode With rx_coreclk & tx_coreclk Enabled
Table 3–3 displays a list of the input and output clock ports available in basic mode.
Table 3–3. Input & Output Ports Available in Basic Mode (Part 1 of 2)
Clock Port Description rx_cruclk Input Input to CRU available as a port when CRU is not trained by the transmitter PLL. inclk Input Input to transmitter PLL available as a port when the transmitter PLL is instantiated. coreclk_out Output Output clock from transmitter PLL equivalent to TX_PLL_CLK. Available as port if transmitter PLL is used. rx_clkout Output Output clock from transceiver. In this mode, RX_CLKOUT is the recovered clock of the respective channel.
Altera Corporation 3–23 January 2005 Stratix GX Transceiver User Guide Basic Mode Clocking
Table 3–3. Input & Output Ports Available in Basic Mode (Part 2 of 2)
Clock Port Description tx_coreclk Input Clocks write port of transmitter phase compensation FIFO module. Available as optional port in the Quartus II MegaWizard® Plug-In Manager. Must be frequency matched to TX_PLL_CLK. If not available as a port, this is fed by CORECLK_OUT through logic array routing. rx_coreclk Input Clocks read port of Receiver phase compensation FIFO module. Available as optional port in the Quartus II MegaWizard Plug-In Manager. If not available as a port, this is fed by RX_CLKOUT through logic array routing.
Basic Mode Inter-Transceiver Block Clocking
This section describes guidelines for using transceiver interface clocking between the device logic array and transceiver channels when multiple transceiver blocks are active. Depending on the mode supported by the Stratix GX devices, each transceiver block has a different transceiver-to- device-interface clocking. Different input and output clocks are available based on the options provided by the MegaWizard Plug-In Manager’s built-in functions. Support for the number of channels offered varies depending on which Stratix GX device is selected. Because of the various configurations of input and output clocks, you must carefully consider the clocking schemes between transceiver blocks to prevent pitfalls later in the design cycle.
One of the clocking interfaces to consider while designing with Stratix GX devices is the transceiver-to-FPGA interface. This clocking scheme is further classified as the FPGA to transmitter channel and the receiver channel to the FPGA.
In basic mode, the read port of the transmitter phase compensation FIFO module is either clocked by the CORECLK_OUT or the TX_CORECLK signal. The constraint on using TX_CORECLK is that the clock must be frequency locked to the read clock of the transmitter phase compensation FIFO module. Synchronous data transfers for a multi-transceiver block configuration can be accomplished by using the TX_CORECLK port. The TX_CORECLK of multi-transceiver blocks is connected to a common clock domain either from a single CORECLK_OUT signal or from a device system clock domain. This scheme is shown in Figure 3–22.
3–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–22. Example of a Multi-Transceiver Block Device to Transmitter Interface Clocking Scheme in Basic Mode
Altera Gigabit Transceiver Block PLD
coreclk_out[0]
tx_in_0[15..0] Transceiver Block 0 tx_coreclk[0]
coreclk_out[1] tx_in_1[15..0] Transceiver Block 1 tx_coreclk[1]
PLD Transmit Data Clock Domain coreclk_out[2]
tx_in_2[15..0] Transceiver Block 2 tx_coreclk[2]
coreclk_out[3] tx_in_3[15..0] Transceiver Block 3 tx_coreclk[3]
When TX_CORECLK is not enabled, the Quartus II software automatically routes the CORECLK_OUT signal to the write clock of the phase compensation FIFO module using a global, regional, or fast regional resource. In a multi transceiver block configuration, this routing can lead to timing violations because the coreclk_out per transceiver block cannot guarantee phase relationship. Therefore, the TX_CORECLK with a common clock is recommended for synchronous transmission.
Altera Corporation 3–25 January 2005 Stratix GX Transceiver User Guide Basic Mode Clocking
Another inter-transceiver block consideration is the selection of the dedicated REFCLKB pin. Stratix GX channels are arranged in banks of four, or transceiver blocks. Each transceiver block is able to share a common reference clock through the inter-transceiver lines. You can reduce the Stratix GX logic array clock usage by using the inter- transceiver lines. The inter-transceiver lines are used when a REFCLKB input port from one transceiver block or channel drives any other transceiver blocks or channels. The Quartus II software automatically determines the inter-transceiver line usage.
When determining the location of REFCLKB pins, you should consider what is fed by the chosen pin. Table 3–4 shows the available inter-transceiver lines, along with the transceiver block that drives them. This information is based on the number of transceiver channels in the Stratix GX device.
Table 3–4. REFCLKB to IQ Line Connections
REFCLKB in Channels in IQ Line Driven by Channel Density Transceiver Block Transceiver Block REFCLKB Number 8 channels 0 [3:0] IQ2 (EP1SGX10) 1 [7:4] IQ0 16 channels 0 [3:0] N/A (EP1SGX25) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 20 channels 0 [3:0] N/A (EP1SGX40) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 4 [19:16 N/A
Figure 3–23 shows the transceiver routing with respect to inter- transceiver lines for the EP1SGX25 device. It is important to use this information when placing REFCLKB pins. For example, if a REFCLKB pin is used and is required to feed a transmitter PLL using an inter- transceiver line, the REFCLKB pin cannot be in transceiver block 1, because IQ2 feeds only the receiver PLLs.
3–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–23. Inter-Transceiver Line Connections for EP1SGX25 Device
Transceiver Block 0
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 IQ0 IQ1 IQ2 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 1
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
16 Transceiver Block 2 PLD Global Clocks IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 3
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Altera Corporation 3–27 January 2005 Stratix GX Transceiver User Guide Basic Mode Clocking
Figure 3–24 shows the transceiver routing with respect to inter- transceiver lines for the EP1SGX40G Device. This device has an extra transceiver block (4), which is in the middle of the row of transceiver blocks. This information is important when placing REFCLKB pins. For example, if a REFCLKB pin must feed a transmitter PLL using an inter- transceiver line, the REFCLKB pin cannot be in transceiver block 1, because IQ2 feeds only the receiver PLLs. REFCLKB is used for transceiver block 2 and transceiver block 3.
Figure 3–24. Inter-Transceiver Line Connections for the EP1SGX40G Device
Transceiver Block 0
IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 1 IQ0 IQ1 IQ0 IQ1 IQ2 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 4 PLD IQ0 Global IQ1 Clocks Global Clks, I/O Bus, Gen Routing TX PLL refclkb 16 /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
Transceiver Block 2 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 3 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 4 4 Global Clks, I/O Bus, Gen Routing Receiver PLLs
3–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Basic Mode Altera recommends that the Stratix GX transceiver block be instantiated and parameterized through the altgxb megafunction in the MegaWizard MegaWizard Plug-In Manager. The MegaWizard Plug-In Manager offers Plug-In a graphical user interface (GUI) that organizes the altgxb options into easy-to-use sections. The wizard also sets the proper ports and parameters automatically, based on the options and parameters you select. Invalid settings are automatically flagged in the wizard to help prevent illegal configurations. The MegaWizard Plug-In Manager does not provide access to any options that do not apply to basic mode.
Basic Mode MegaWizard Plug-In Manager Considerations
Each altgxb megafunction instantiation uses one or more transceiver blocks, based on the number of channels that you select. There are four channels per transceiver block. If a MegaWizard Plug-In Manager instantiation uses fewer than four channels, the remaining channels in that transceiver block are not available for use.
Each MegaWizard Plug-In Manager instantiation must have similar functionality and data rates. If transceiver blocks that differ in functionality and/or data rates are required, you can create separate instantiations for each transceiver block.
As mentioned in the clocking section, the MegaWizard Plug-In Manager displays the configuration of the altgxb megafunction. This diagram changes dynamically based on the selected mode, options and clocking schemes.
Basic Mode altgxb MegaWizard Options
Figure 3–25 through 3–31 show where you select the options for a basic mode configuration in the MegaWizard Plug-In Manager pages.
Altera Corporation 3–29 January 2005 Stratix GX Transceiver User Guide Basic Mode MegaWizard Plug-In
Figure 3–25. MegaWizard Plug-In Manager - ALTGXB (Page 3 of 9) - General (1) Notes (1)–(5)
Notes to Figure 3–25: (1) Basic protocol mode supports duplex, receive- only, or transmitter-only operation modes. (2) This value can be from 1 to the maximum number of channels available on the device. (3) The correct channel width setting depends on whether you are using 8B/10B decoding. With 8B/10B, 8 bits is single width, 16 bits is double width. Without 8B/10B, 8 bits is single width, 16 bits is double width, 10 bits is single width, and 20 bits is double width. (4) Refer to the Stratix GX Analog Description chapter for more information. (5) The rxdigitalreset port resets the digital blocks in the receiver channel. Each active receiver channel has its own digital reset. The txdigitalreset port resets the digital blocks of the transmitter channel. Each active transmitter channel has its own digital reset. The rxanalogreset port resets the receiver’s analog circuits including the receiver PLL. Each active receiver channel has its own analog reset. The pll_areset port resets the entire transceiver block (all receiver and transmitter digital and analog circuits including receiver and transmitter PLLs). The pllenable port enables the entire transceiver block; if deasserted, the entire transceiver block is held in the reset condition. (6) The pll_locked active high signal that indicates that the transmitter PLL is locked to the reference input clock.
3–30 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–26. MegaWizard Plug-In Manager - ALTGXB (Page 4 of 9) - General (2) Notes (1), (2)
Notes to Figure 3–26: (1) For more information, refer to the Loopback Modes chapter. (2) For more information, refer to the Stratix GX Built-In Self Test (BIST) chapter.
Altera Corporation 3–31 January 2005 Stratix GX Transceiver User Guide Basic Mode MegaWizard Plug-In
Figure 3–27. MegaWizard Plug-In Manager - ALTGXB (Page 5 of 9) - Receiver (1) Notes (1), (2)
Notes to Figure 3–27: (1) You can enable or disable 8B/10B. With 8B/10B active, data width must be 8-bits or 16-bits. (2) For more information, refer to the Stratix GX Analog Description chapter. (3) rx_enacdet: supports word aligner to byte align to the word alignment pattern. When rx_enacdet is held high, the word aligner aligns to the byte boundary, if the comma is detected. If this option is de-selected, the word aligner is not active, but the pattern detect signal is still functional. Refer to the word aligner section for further details. (4) Manual bit-slipping mode lets you control the word aligner’s shift register directly via the rx_bitslip port. A low to high transition on the rx_bitslip port enables the word aligner’s shift register to slip one bit. For example, if a 3-bit shift is required to align the incoming byte, then rx_bitslip must be toggled low, high, low, high, low, high. The rx_bitslip port can be left in the high or low position after the above sequence. (5) The word alignment pattern size must be set to 16-bits if using 8-bits or 16-bits data bus size with 8B/10B off. With 8B/10B on and a data width of 8-bits or 16-bits, the pattern size must be 7-bits or 10-bits. The 7-bit mode is for the pattern detect module. Word alignment is still done on the 10-bit pattern, even in a 7-bit mode. (6) Flips the word alignment bit order. If checked, the right-most bit is the MSB, otherwise the right-most bit is the LSB. This option is used in conjunction with the receiver and transmitter bit-flip options to ensure that the MSB is transmitted/received first in the serial stream. Not available if 8B/10B is used.
3–32 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–28. MegaWizard Plug-In Manager - ALTGXB (Page 6 of 9) - Receiver (2) Notes (1), (2)
Notes to Figure 3–28: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) Data rate versus input clock frequency must adhere to the set multiplication factor of 2, 4, 5, 8, 10, 16, 20 of the input clock. Multiplication factors of 2, 4, 5 must use the dedicated refclkb pins. The multiplication factor of 2 also requires that the receiver PLL be trained by the transmitter PLL.
Altera Corporation 3–33 January 2005 Stratix GX Transceiver User Guide Basic Mode MegaWizard Plug-In
Figure 3–29. MegaWizard Plug-In Manager - ALTGXB (Page 7 of 9) - Receiver (3) Notes (1)–(5)
Notes to Figure 3–29: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) The rx_clkout signal is a recovered clock output from individual receiver channels. One rx_clkout signal is available per channel. (3) The rx_locked signal is an active low signal that indicates that the receiver PLL is phase locked to the reference clock. In data mode, this signal might be deasserted because the phase is being locked to the data and not the reference clock. (4) The rx_syncstatus signal indicates the status of the word aligner. Refer to the section “Word Aligner” on page 3–2 for more information. (5) The rx_patterndetect signal is an active high signal that signifies that the comma appears in the current byte boundary of the incoming data stream.
3–34 Altera Corporation Stratix GX Transceiver User Guide January 2005 Basic Mode
Figure 3–30. MegaWizard Plug-In Manager - ALTGXB (Page 8 of 9) - Transmitter Note (1)
Notes to Figure 3–30: (1) For more information, refer to the Stratix GX Analog Description chapter.
Altera Corporation 3–35 January 2005 Stratix GX Transceiver User Guide Basic Mode MegaWizard Plug-In
Figure 3–31. MegaWizard Plug-In Manager - ALTGXB (Page 9 of 9) - Summary
3–36 Altera Corporation Stratix GX Transceiver User Guide January 2005 4. SONET Mode
Introduction One of the most common serial backplanes in the communications or telecom area is the SONET/SDH interface. For SONET/SDH applications the synchronous transport signal STS-48 and Synchronous Transport Module -16 (STM -16) are becoming popular SONET backplanes.
Transceiver blocks provide an implementation of SONET/SDH backplanes. The serial data range over 40'' of FR4 printed circuit board support a STS-12/STS-48 and STS-192 standards data range. You can implement many functions associated with SONET/SDH processing. SONET/SDH backplanes are not designed to a specific standard because different telecom manufacturers have developed their own proprietary buses. The backplane transceiver in a SONET/SDH application requires two types of features: protocol-specific functions and electrical features. Transceiver blocks provide both of these features to a limited extent. One example is the protocol feature using A1A2 or A1A1A2A2 for word alignment.
SONET mode supports a subset of the transceiver blocks to allow for customizable configuration. The channel aligner, rate matcher, and the 8B/10B encoder/decoder features are not available in this mode. This chapter describes the supported digital architecture, clocking schemes, and software implementation in SONET mode. Figure 4–1 shows a block diagram of a transceiver channel configured in SONET mode.
Stratix® GX devices offer the following SONET/SDH features:
■ Serial data rate range from 614 Mbps to 3.1875 Gbps (non-encoded) ■ Input reference clock range from 38.375 to 650 MHz ■ Supports parallel interface width of 8 or 16 bits ■ Word aligner supports 16-bit or bit-slip mode
Altera Corporation 4–1 January 2005 SONET Mode Receiver Architecture
Figure 4–1. Block Diagram of Transceiver Channel Configured in SONET Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte Compensation 8B/10B Serializer Encoder FIFO Buffer
Receiver Transmitter
SONET Mode Figure 4–2 shows the digital components of the Stratix GX receiver that Receiver are active in SONET mode. Architecture
Figure 4–2. Block Diagram of Receiver Digital Components in SONET Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Receiver
Word Aligner
For embedded clocking schemes, the clock is recovered from the incoming data stream based on transition density of the data. This feature eliminates the need to factor in receiver skew margins between the clock and data. However, with this clocking methodology, the word boundary of the re-timed data can be altered. Stratix GX transceivers offer an
4–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
embedded word alignment circuit to use in conjunction with the pattern detector to align the word boundary of the re-timed data to a specified comma. In SONET mode, this embedded circuit is configured to manual alignment mode consisting of 16-bit and bit-slip modes.
The word aligner is composed of a pattern detector, manual alignment controller, bit-slipper circuitry, and synchronization state machines. Depending on the configuration, these components work in conjunction with or independently of one another. The word aligner cannot be bypassed, but if the rx_enacdet signal is held low, the word aligner does not alter the word boundary. Figure 4–3 shows the various components of the word aligner in SONET mode. The functionality is described in the following sections.
Figure 4–3. Stratix GX Word Aligner Components
Word Aligner
Pattern Manual Detector Alignment Mode
SONET Bit-slip SONET Mode Mode Mode
A1A2 A1A1A2A2 A1A2 A1A1A2A2 Mode Mode Mode Mode
Pattern Detector Module The pattern detector matches the comma to the current byte-boundary, as specified in the MegaWizard® Plug-In Manager. If the comma is found, the optional rx_patterndetect signal is asserted for the duration of one clock cycle to signify that the comma exists in the current word boundary. The pattern detector module only indicates that the signal exists and does not modify the word boundary. Modification of the word boundary is discussed later in the word alignment and synchronization sections.
Altera Corporation 4–3 January 2005 Stratix GX Transceiver User Guide SONET Mode Receiver Architecture
Manual SONET Alignment Mode (2 Consecutive 8-bit Characters (A1A2) or 4 Consecutive 8-bit Characters (A1A1A2A2) The 2 consecutive 8-bit characters, A1A2 SONET Section Overhead Framing Bytes, are used as the comma in 16-bit pattern mode.
The 16-bit comma is specified in the MegaWizard Plug-In Manager. The comma has the bit orientation of [MSB..LSB]. A1 represents the least significant byte, which consist of bits [7..0], and A2 represents the most significant byte consisting of bits [15..8]. The comma, or alignment pattern, must be specified as [A2,A1] in the MegaWizard Plug-In Manager. If “Flip Word Alignment bits” is selected, the ordering of the alignment pattern is [LSB..MSB] for the bit ordering and [A1, A2] for the byte ordering. Only the positive disparity of the comma is detected in the mode. Table 4–1 shows several word alignment patterns based on different bit transmission orders and whether the receiver word alignment bit flip option is checked. The bit transmission order assumes that if double width mode is used, the LSB is transmitted first, followed by the MSB.
Table 4–1. Word Alignment Patterns for SONET Mode
Bit Transmission Order Word Alignment Bit Flip Word Alignment Pattern (at the Source) MSB to LSB On 1111011000101000 (hex F628) MSB to LSB Off 0001010001101111 (hex 146F) LSB to MSB Off 0010100011110110 (hex 28F6)
In SONET mode, the word aligner either aligns to two consecutive 8-bit characters (A1A2) or four consecutive 8-bit characters (A1A1A2A2). The rx_a1a2size[] signal differentiates between the 2 and 4 consecutive modes. The word aligner aligns to the A1A2 pattern when the rx_a1a2size[] is held low, or to the A1A1A2A2 when rx_a1a2size[] is high. If the optional rx_a1a2size signal is not selected, the word aligner defaults to the A1A2 mode. An optional signal, rx_a1a2sizeout[], can also be enabled to send the state of the rx_a1a2[] signal as seen by the word aligner into the device logic array. The value of the signal is forwarded to the device, along with the byte that was in the word aligner when the rx_a1a2size[] signal was sampled.
4–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
In SONET mode, the byte boundary is locked after the first comma is detected, and the boundary is aligned after the rising edge of the rx_enacdet[] signal. If the byte boundary changes the rx_enacdet[] signal must be deasserted and reasserted to reset the alignment circuit. This feature is valuable in SONET because the data is scrambled and not encoded. The comma can exist across byte boundaries and can trigger a false re-alignment. In SONET, the byte boundary must be aligned and locked at the beginning of a SONET frame, because the A1A2 comma resides in the framing section at the beginning of the transport overhead.
Because the SONET frame is a set size, the occurrence of the A1A2 framing bytes is anticipated. The actual A1A2 framing bytes are checked with a counter (A1A2 framing bytes occur every 125 µs based on an STS- 1 Frame and a rate of 51.84 Mbps).
As stated earlier, at the rising edge of the rx_enacdet[], the word aligner locks onto the first comma detected. In this scenario, the rx_patterndetect[] is asserted for one clock cycle to signify that the comma has been aligned. Also, the rx_syncstatus[] signal is asserted for a clock cycle to signify that the word boundary has been synchronized. After the word boundary has been locked, regardless of whether the rx_enacdet[] is held high or low, the rx_syncstatus[] signal asserts itself for one clock cycle whenever the comma is detected across a different byte boundary. The rx_syncstatus[] operates in this re-synchronization state until a rising edge is detected on the rx_enacdet[].
Figure 4–4 shows an example of how the word aligner signals interact in SONET alignment mode for an A1A2 pattern. In this example, a SONET A1A2 Framing pattern is used (16'b0001010001101111). In this case, the A1 is represented by 8'b01101111, and A2 is represented by 8'b00010100.
Altera Corporation 4–5 January 2005 Stratix GX Transceiver User Guide SONET Mode Receiver Architecture
Figure 4–4. Word Aligner Symbols Interacting in SONET A1A2 Manual Alignment Mode
n n+1 n+2 n+3 n+4 n+5 n+6
rx_recovclockout
rx_word_align_out 01101111 00010100 1111111101000110 00000001 01101111 00010100
rx_enacdet
rx_patterndetect
rx_syncstatus
rx_a1a2size
The rx_a1a2size signal is held low. This low signal sets the SONET alignment mode to A1A2. Because rx_enacdet is toggled high at time n, the aligner locks to the boundary of the next present comma. Additionally, the A1 comma appears on the rx_word_align_out port during this period. At time n+1, the A2 comma appears on the rx_word_align_out port. Because the comma exists, the rx_patterndetect and rx_syncstatus signals are asserted for one clock cycle to signify that the A1A2 comma has been detected and that the word boundary has been locked. The A1A2 comma appears again across word boundaries during periods n+2, n+3, and n+4. The rx_enacdet signal is held high, but the word aligner does not re-align the byte boundary. Instead, the rx_syncstatus signal is asserted for one clock cycle to signify a re-synchronization condition. You must deassert and reassert the rx_enacdet signal to re-trigger the word aligner. The next transition occurs at time n+5, where rx_enacdet is deasserted and the A1 pattern is present on the rx_word_align_out port. At time n+6, the A2 pattern is present on the rx_word_align_out port. The word aligner then asserts the rx_patterndetect signal for one clock cycle to flag the detection of the comma on the current word boundary.
Manual Bit-Slipping Alignment Mode Word alignment is achieved by enabling the manual bit-slip option in the MegaWizard Plug-In Manager. With this option enabled, the transceiver can shift the word boundary by one bit in every parallel clock cycle. Bits are shifted from the MSB to LSB direction. This shift occurs every time the bit-slipping circuitry detects a rising edge of the rx_bitslip[] signal. Each time a bit is slipped, the bit that arrived at the receiver earlier is skipped. When the word boundary matches what is specified as the
4–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
comma, the rx_patterndetect[] signal is asserted for one clock cycle. You must implement the logic in the device logic array to control the bit-slip circuitry.
This scheme is useful if the comma changes dynamically when the Stratix GX device is in user mode. Because the controller is implemented in the logic array, a custom controller can be built to dynamically change the comma without needing to reprogram the Stratix GX device. The pattern detect circuitry matches only the pattern that is specified in the MegaWizard Plug-In Manager and is not dynamically adjustable.
Figure 4–5 shows an example of how the word aligner signals interact in the manual bit-slip alignment mode. In this example, 8'b00111100 is specified as the comma, and an 8'b11110000 value is held at the rx_in port. Every rising edge on the rx_bitslip port causes the rx_word_align_out data to shift one bit from the MSB to the LSB. At time n+2, the 8'b11110000 data is shifted to a value of 8'b01111000. At this state the rx_patterndetect is held low, because the specified comma does not exist in the current word boundary. The rx_bitslip is disabled at time n+3 and re-enabled at time n+4. The output of the rx_word_align_out now matches the specified comma, so the rx_patterndetect is asserted for one clock cycle. At time n+5, the rx_patterndetect is still asserted because the comma still exists in the current word boundary. Finally, at time n+6, the rx_word_align_out boundary is shifted again and the rx_patterndetect signal is deasserted to signify that the word boundary does not contain the comma.
Figure 4–5. Word Aligner Symbols Interacting in Manual Bit-Slip Mode
n n+1 n+2 n+3 n+4 n+5 n+6
rx_recovclockout
rx_in 11110000
rx_word_align_out 11110000 01111000 00111100 00011110
rx_bitslip
rx_patterndetect
Altera Corporation 4–7 January 2005 Stratix GX Transceiver User Guide SONET Mode Receiver Architecture
Byte Deserializer
The byte deserializer module further reduces the speed that the FPGA logic array must achieve in order to meet performance. The possible division factors are 8 and 16. This requirement results in a byte or double byte data width in the PLD logic array.
In SONET mode, the maximum output bus width is 22 bits. If the input includes data and control signals, the data and the control signals are deserialized to include double the data bits and 2 bits of each control signal, one for the MSB and one for the LSB. This case is shown when in SONET mode where the inputs to the Byte Deserializer are datain[7..0], rx_syncstatus, rx_patterndetect, and rx_a1a2sizeout. These total 11 input signals feeding the byte deserializer and 22 output signals are fed to the FPGA logic array. The signals are sent into the logic array as two 11-bit buses. The aggregate bandwidth does not change by use of the Byte Deserializer because the logic array data width is doubled.
Figure 4–6 demonstrates input and output signals of the byte deserializer when deserializing an 8-bit data input to 16-bits. In this case, the finishing alignment pattern A2 (00010100) shown as 'B' is located in the MSB of the 16-bit output and this is reflected with patterndetect [1] going high. The output of the byte deserializer is BA, DC, FE, and so on. This example assumes that the word alignment bit-flip option is unchecked (OFF), and that the transmitter and receiver bit-flip option is checked (ON) to adhere to the MSB transmitted first option.
Figure 4–6. Receiver Byte Deserializer in 8/16-Bit Mode With Finishing Alignment Pattern in MSB
inclk
A B C D E F
data_in[7..0] 01101111 00010100 11000110 11110001 10101010 11001100
BA DC
data_out[15..0] xxxxxxxxxxxxxxxxxxxx 0001010001101111 1111000111000110
patterndetect[0]
patterndetect[1]
4–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–7 demonstrates the alternate case of the finishing alignment pattern found in the LSB of the 16-bit output. Correspondingly patterndetect[0] goes high. In this case, the output is BA, DC, FE, and so on.
Figure 4–7. Receiver Byte Deserializer in 8/16-Bit Mode with Finishing Alignment Pattern in LSB
inclk
A B C D E F
data_in[7..0] 00010100 11000110 11110001 10101010 11001100 11111000
BA DC
data_out[15..0] xxxxxxxx01101111 11000110 00010100 10101010 11110001
patterndetect[0]
patterndetect[1]
If necessary, you might implement logic to perform byte position alignment once data enters the logic array, as seen in Figure 4–8. In this example, the byte position selection logic determines the proper byte position based on the pattern detect signal.
Altera Corporation 4–9 January 2005 Stratix GX Transceiver User Guide SONET Mode Receiver Architecture
Figure 4–8. Receiver Byte Deserializer Data Recovery in Logic Array
Gigabit Transceiver Block Logic Array
rx_out[19..10] rx_out_post[19..10] DQ 10 10 rx_out_post[19..0] 10 rx_out_align[19..0] Phase 10 Compensation 20 FIFO Buffer {rx_out[9..0], rx_out_post[19..10]}
rx_out[9..0] rx_out_post[9..0] DQ 10 10
Byte Boundary Selection Logic
Receiver Phase Compensation FIFO Module
The receiver phase compensation FIFO module is located at the FPGA logic array interface in the receiver block and is four words deep. The FIFO module compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
In SONET mode, the write port is clocked by the recovered clock from the CRU. The rate of this clock is reduced by half if the byte deserializer is used. The read clock is clocked by rx_coreclk.
You can select rx_coreclk as an optional receiver input port that can also accept a clock supply. The clock that feeds the rx_coreclk must be derived from the rx_clkout of its associated receiver channel. The receiver phase compensation FIFO buffer can only account for phase differences.
In SONET mode, if you do not select the rx_clkout port, the read clock of the receiver phase compensation FIFO module, clocked by rx_coreclk, is fed by rx_clkout. An FPGA global clock, regional clock, or fast regional clock resource is required to make the connection
4–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
for the read clock. Refer to “SONET Mode Channel Clocking” on page 4–12 or the block diagram in the MegaWizard Plug-In Manager for more information on the clock structure in a particular mode.
The Receiver Phase Compensation FIFO module is always used and cannot be bypassed.
SONET Mode Figure 4–9 shows a diagram of the digital components of the transmitter. The rest of this section describes the active components of the transmitter, Transmitter which are the phase compensation FIFO buffer and the byte serializer. Architecture The 8B/10B decoder is not active during SONET mode.
Figure 4–9. Block Diagram of the Transmitter Digital Components in SONET Mode
Analog Section Digital Section
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Transmitter
Transmitter Phase Compensation FIFO Buffer
The transmitter phase compensation FIFO buffer is located at the FPGA logic array interface in the transmitter block and is four words deep. The phase compensation FIFO module compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
The read port of the phase compensation FIFO buffer is clocked by the transmitter PLL clock. The write clock is clocked by tx_coreclk. You can select the tx_coreclk as an optional transmitter input port to supply a clock to. In this case, you must ensure that there is no frequency difference between the tx_coreclk and the transmitter PLL clock. The transmitter phase compensation FIFO module can only account for phase differences.
If the tx_coreclk is not selected as an optional input transmitter port, tx_coreclk is fed by coreclk_out. This connection occurs using the logic array routing. In this case, the software defaults to using an FPGA global clock, regional clock, or fast regional clock resource.
Altera Corporation 4–11 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
The Transmitter Phase Compensation FIFO module is always used and cannot be bypassed. The input to the Transmitter Phase Compensation FIFO module is the data from the FPGA logic array.
Byte Serializer
In SONET mode, the Byte Serializer in the transmitter block takes in a 16-bit input from the phase compensation FIFO module and serializes it to 8 bits. It transmits the least significant byte to the most significant byte. The transmitter digital reset must always be used to reset the Byte Serializer FIFO module pointers whenever an unknown state is encountered, for example, during periods when the transmitter PLL loses lock. Refer to Chapter 8, Reset Control and Power Down, for further details on the reset sequence.
Figure 4–10 demonstrates input and output signals of the byte serializer when serializing a 16 bit input to 8 bits. The tx_in[] signal is the input from the FPGA logic array that has already passed through the Transmitter Phase Compensation FIFO module.
Figure 4–10. Transmitter Byte Serializer in 8- to 16-Bit Mode
D1 D2 D3
datain[15..0] 0001010001101111 1100011011110001 1010101010110011
dataout[7..0] xxxxxxxx xxxxxxxx 01101111 00010100 11110001 11000110
LSB MSB LSB MSB
D1 D2
The LSB is transmitted before the MSB in the transmitter byte serializer. Figure 4–10 shows the order of data transmitted. For the input of D1, the output is D1LSB and then D1MSB. The byte serializer is selected in the MegaWizard Plug-In Manager when a 16-bit channel width is selected.
SONET Mode SONET Mode Channel Clocking Clocking This section covers describes the internal clocking and the external clocks of the transceiver in SONET mode. By default, the MegaWizard Plug-In Manager parameterizes the altgxb megafunction with the clock configuration shown in Figure 4–11.
4–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–11. Default Configuration of altgxb in SONET Mode
In Figure 4–11, the altgxb megafunction is configured so that the train receiver PLL with transmitter PLL is enabled. The transmitter PLL is fed from an inclk port, which can be fed from a dedicated REFCLKB, Global clock, Regional clock, or Fast Regional clock source. The receiver logic is clocked by the recovered clock from the clock recovery unit, rx_clkout. This recovered clock is also fed into the FPGA so that, in a multi-crystal environment, some level of clock domain decoupling can be implemented to interface with a system clock. On the transmitter channel, the output of the transmitter PLL, coreclk_out, is sent into the logic array and also loops back to clock the write side of the transmit phase compensation FIFO module.
The train receiver PLL CRU clock from the transmitter PLL feature can be disabled in the altgxb MegaWizard Plug-In. Deselecting this option enables an additional rx_cruclk input reference clock port for the receiver PLL. This feature supports additional multiplication factors for the receiver PLL and allows for the separation of receiver and transmitter reference clocks. This separation is required if the output reference clock frequency from the transmitter PLL exceeds the 325 MHz phase
Altera Corporation 4–13 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
frequency detector of the receiver PLL. For more information on this feature, refer to the Stratix GX Analog Description chapter. This configuration is shown in Figure 4–12.
If double width is used (16-bit bus) and the data rate is above 2,600 Mbps, the trained receiver PLL clock from the transmitter PLL must be turned off, because the output clock from the transmitter PLL exceeds the 325- MHz limit on the receiver PLL input clock, if the input clock is fed from any non-REFCLKB pin. REFCLKB pins have a 650-MHz limit.
Figure 4–12. altgxb Megafunction in SONET Mode With Train Receiver CRU From Transmitter PLL Disabled
This configuration contains an independent rx_cruclk, which feeds the receiver PLL reference clock. This input clock port is only available when the receiver PLL is not trained by the transmitter PLL. One rx_cruclk is associated with a channel. If four channels are active, there are four rx_cruclks.
The rx_clkout is the recovered clock from the associated receiver channel. An rx_clkout is available for each receiver channel that is used. This clock is used to clock the write port of a rate matching FIFO module. The read port of the FIFO module is clocked by the coreclk_out or PLD clock.
4–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
The coreclk_out is the output from the transmitter PLL. A coreclk_out is available for each transceiver block that is used. Altera® recommends clocking the logic that is feeding the transmitter with this clock.
The read clock of the receiver phase compensation FIFO module and the write clock of the transmitter phase compensation FIFO module are optionally enabled to manually feed in a clock from the FPGA logic array. You use these options to optimize the global clock usage. For instance, if all transmitter channels between transceiver blocks are from a common clock domain, the transceiver instantiations use a total of one global resource clock versus one global per transceiver block, if the tx_coreclk option is not enabled.
The same situation can be optimized for the receiver channels in a single crystal synchronous system with the rx_coreclk. Even in a system that is based on a single crystal, the recovered clock can still become asynchronous to the system clock during initialization or long run lengths. As a result, the pointers of the Receiver Phase Compensation FIFO module might overlap and fail to function correctly. In situations where there are long run lengths or no data transmissions, these FIFO modules must be reset by the rxdigitalreset signal.
In multi-crystal environments, individual recovered clocks must drive the read clock of the phase compensation FIFO module. The Quartus® II software does this by default, and you do have to manually make this connection. The rx_coreclk and tx_coreclk must be frequency matched with their respective read and write ports. The phase compensation FIFO module can only correct for phase, not frequency differences. Figure 4–13 shows the clock configuration with these optional input ports enabled.
Altera Corporation 4–15 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
Figure 4–13. altgxb in SONET Mode With rx_coreclk & tx_coreclk Enabled
For reference, the various input and output clock ports are listed in Table 4–2.
Table 4–2. List of Clocking Input & Output Ports Available in SONET Mode (Part 1 of 2)
Clock Port Description rx_cruclk Input Input to CRU available as a port when CRU is not trained by the transmitter PLL. inclk Input Input to the transmitter PLL, available as a port when the transmitter PLL is instantiated. coreclk_out Output Output clock from the transmitter PLL equivalent to TX_PLL_CLK. Available as a port if the transmitter PLL is used.
4–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Table 4–2. List of Clocking Input & Output Ports Available in SONET Mode (Part 2 of 2)
Clock Port Description rx_clkout Output Output clock from transceiver. In this mode, rx_clkout is the recovered clock of the respective channel. tx_coreclk Input Clocks the write port of transmitter phase compensation FIFO module. Available as an optional port in the Quartus II MegaWizard® Plug-In Manager. Must be frequency matched to tx_pll_clk. If not available as a port, this is fed by coreclk_out through logic array routing. rx_coreclk Input Clocks read port of receiver phase compensation FIFO module. Available as an optional port in the Quartus II MegaWizard Plug-In Manager. If not available as a port, this is fed by rx_clkout through logic array routing.
SONET Mode Inter-Transceiver Block Clocking
This section provides guidelines for using transceiver interface clocking between the FPGA logic array and transceiver channels when multiple transceiver blocks are active. Depending on each mode supported by Stratix GX devices, each transceiver block contains different transceiver-to-FPGA interface clocking. Different input and output clocks are available based on the options provided by the Quartus II MegaWizard Plug-In Manager’s built-in functions. The number of supported channels varies based on which Stratix GX device you select. Because of the various configurations of input and output clocks, consider the clocking schemes between inter-transceiver blocks carefully to prevent problems later in the design cycle.
Altera Corporation 4–17 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
One of the clocking interfaces to consider while designing with Stratix GX devices is the transceiver-to-FPGA interface. This clocking scheme is further classified as the FPGA-to-transmitter channel and the FPGA-to-receiver channel to the PLD.
In SONET mode, the read port of the transmitter phase compensation FIFO module is either clocked by the coreclk_out or by the tx_coreclk signal. The constraint on using tx_coreclk is that the clock must be frequency locked to the read clock of the transmitter phase compensation FIFO module. Synchronous data transfers for a multi-transceiver block configuration are accomplished by using the tx_coreclk port. The tx_coreclk of multi-transceiver blocks are connected to a common clock domain either from a single coreclk_out signal or from an FPGA system clock domain. This scheme is shown in Figure 4–14.
4–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–14. Example of a Multi-Transceiver Block FPGA to Transmitter Interface Clocking Scheme in SONET Mode
Altera Gigabit Transceiver Block PLD
coreclk_out[0]
tx_in_0[15..0] Transceiver Block 0 tx_coreclk[0]
coreclk_out[1] tx_in_1[15..0] Transceiver Block 1 tx_coreclk[1]
PLD Transmit Data Clock Domain coreclk_out[2]
tx_in_2[15..0] Transceiver Block 2 tx_coreclk[2]
coreclk_out[3] tx_in_3[15..0] Transceiver Block 3 tx_coreclk[3]
When tx_coreclk is not enabled, the Quartus II software automatically routes the coreclk_out signal to the write clock of the phase compensation FIFO module via a global, regional, or fast regional resource. In multi-transceiver block configuration, this routing might lead to timing violations because the coreclk_out per transceiver block cannot guarantee phase relationship. For this reason, Altera recommends clocking the tx_coreclk with a common clock for synchronous transmission.
Another inter-transceiver block consideration is the selection of the dedicated refclkb pin. Stratix GX channels are arranged in banks of four, or transceiver blocks. Each transceiver block has the ability to share a common reference clock through the inter-transceiver (IQ) lines. The
Altera Corporation 4–19 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
Stratix GX logic array clock usage can be reduced by using the IQ lines. The IQ lines are used when a refclkb input port from one transceiver block or channel drives any other transceiver blocks or channels. The Quartus II software automatically determines the IQ line usage.
When determining the location of refclkb pins, be sure to take into consideration what is fed by the pin you choose. Table 4–3 shows the available IQ lines and which transceiver block refclkb drives them. This capability is based on the number of transceiver channels in the Stratix GX device.
Table 4–3. REFCLKB to Inter-Transceiver Line Connections
REFCLKB in Channels in IQ Line Driven by Channel Density Transceiver Block Transceiver Block REFCLKB Number 8 channels 0 [3:0] IQ2 (EP1S10) 1 [7:4] IQ0 16 channels 0 [3:0] N/A (EP1S25) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 20 channels 0 [3:0] N/A (EP1S40) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 4 [19:16] N/A
Figure 4–15 shows the transceiver routing with respect to inter- transceiver lines. It is important to use this information when placing REFCLKB pins. For example, if a REFCLKB pin is required to feed a transmitter PLL using an IQ line, the REFCLKB pin cannot be in transceiver block 1, because IQ2 only feeds the receiver PLLs.
4–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–15. Inter-Transceiver Line Connections for EP1SGX25 Device
Transceiver Block 0
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 IQ0 IQ1 IQ2 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 1
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 2 16
PLD Global Clocks IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 3
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Altera Corporation 4–21 January 2005 Stratix GX Transceiver User Guide SONET Mode Clocking
Figure 4–16 shows the transceiver routing with respect to IQ lines for the EP1SGX40G device. This device has an extra transceiver block (transceiver block 4), in the middle of the other transceiver blocks, as shown. Again, this information is important when determining where to place REFCLKB pins. For example, if a REFCLKB pin is needed to feed to a transmitter PLL using an IQ line, the pin cannot be in transceiver block 1 because IQ2 feeds only the receiver PLLs.
Figure 4–16. IQ Line Connections for EP1SGX40G Device
Transceiver Block 0
IQ0 IQ1 Global Clks, I/O Bus, Gen Routing Transmitter PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 1 IQ0 IQ1 IQ0 IQ1 IQ2 Global Clks, I/O Bus, Gen Routing Transmitter PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 4 PLD IQ0 Global IQ1 Global Clks, I/O Bus, Gen Routing Transmitter Clocks PLL refclkb 16 /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
Transceiver Block 2 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing Transmitter PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 3 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing Transmitter refclkb PLL /2
IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
4–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
SONET Mode This section describes the altgxb megafunction options in the MegaWizard Plug-In Manager for SONET mode. Altera recommends MegaWizard that the Stratix GX transceiver block be instantiated and parameterized Plug-In Manager through the altgxb megafunction in the MegaWizard Plug-In Manager. The Quartus II MegaWizard Plug-In Manager offers a Graphical User Interface (GUI) that organizes the altgxb options in easy to use sections. The MegaWizard Plug-In Manager also sets the proper ports and parameters automatically based on the selected options and parameters. Invalid settings are automatically flagged in the MegaWizard Plug-In Manager to help prevent illegal configurations. The MegaWizard Plug-In Manager also grays out any options that do not apply to SONET mode.
Although you can instantiate the Stratix GX block directly by calling out the altgxb megafunction, Altera recommends using the MegaWizard Plug-In Manager to instantiate the altgxb megafunction to reduce the chance of invalid settings.
SONET Mode MegaWizard Considerations
Each altgxb megafunction instantiation uses one or more transceiver blocks based on the number of channels that you select. There are four channels per transceiver block. If a MegaWizard Plug-In Manager instantiation uses fewer than four channels, the remaining channels in that transceiver block are not available for use.
Each MegaWizard Plug-In Manager instantiation must have similar functionality and data rates. To have transceiver blocks that differ in functionality and/or data rates, you can create a separate instantiation for each transceiver block.
As mentioned in the clocking section, the MegaWizard Plug-In Manager displays the configuration of the altgxb megafunction. This diagram changes dynamically based on the selected mode, options, and clocking schemes.
SONET Mode altgxb MegaWizard Options
Figures 4–17 through 4–22 show where you select the options for a SONET mode configuration in the MegaWizard Plug-In Manager pages.
Altera Corporation 4–23 January 2005 Stratix GX Transceiver User Guide SONET Mode MegaWizard Plug-In Manager
Figure 4–17. MegaWizard Plug-In Manager - ALTGXB (Page 3 of 9) - General (1) Notes (1)–(5)
Notes to Figure 4–17: (1) SONET protocol mode supports duplex, receiver-only, or transmitter-only operation modes. (2) Valid numbers are 1 to Max Channels available on the device. The Quartus II software automatically assigns the channels to a transceiver block unless input/output pin assignments are made to the channel’s HSSIO input and output pins. (3) 8 bits is single width and 16 bits is double width. (4) Refer to the Stratix GX Analog Description chapter for more information. (5) The rxdigitalreset port resets the digital blocks in the receiver channel. Each active receiver channel contains its own digital reset. The txdigitalreset port resets the digital blocks of the transmitter channel. Each active transmitter channel contains its own digital reset. The rxanalogreset port resets the receiver's analog circuits including the receiver PLL. Each active receiver channel contains its own analog reset. The pll_areset port resets the entire transceiver block (all receiver and transmitter digital and analog circuits including receiver and transmitter PLLs). If you send the pllenable signal low, the entire transceiver block is held in reset conditions. (6) The pll_locked active high signal indicates that the transmitter PLL is locked to the reference input clock.
4–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–18. MegaWizard Plug-In Manager - ALTGXB (Page 4 of 9) - General (2) Notes (1), (2)
Notes to Figure 4–18: (1) For more information, refer to the Loopback Modes chapter. (2) For more information, refer to the Stratix GX Built-In Self Test (BIST) chapter.
Altera Corporation 4–25 January 2005 Stratix GX Transceiver User Guide SONET Mode MegaWizard Plug-In Manager
Figure 4–19. MegaWizard Plug-In Manager - ALTGXB (Page 5 of 9) - Receiver (1) Notes (1)–(5)
Notes to Figure 4–19: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) The rx_enacdet port lets the word aligner byte align to the word alignment pattern (active high synchronous signal). The signal must go low then high to trigger word re-alignment. If this option is de-selected, the word aligner is not active, but the pattern detect signal is still functional. (3) Manual bit-slipping mode lets you control the word aligner’s shift register directly via the rx_bitslip port. A low-to-high transition on rx_bitslip port enables the word aligner’s shift register to slip one bit. For example, if a 3-bit shift is required to align the incoming byte, rx_bitslip must be toggled low, high, low, high, low, and high. The rx_bitslip can be left in the high or low position after the above sequence. (4) The word alignment pattern size in SONET mode is always set to 16-bits, and the pattern must be set to 1111011000101000 (F628) if “flip word alignment pattern bits” is set or 0001010001101111 (146F) otherwise, regardless of whether the incoming pattern is an A1/A2 or A1/A1/A2/A2. (5) Flips the word alignment bit order. If checked, the rightmost bit is the MSB, otherwise the rightmost bit is the LSB. Used in conjunction with receiver and transmitter bit flip options to ensure that the MSB is transmitted and received first in the serial stream.
4–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–20. MegaWizard Plug-In Manager - ALTGXB (Page 6 of 9) - Receiver (2) Notes (1)–(3)
Notes to Figure 4–20: (1) Flips the bit ordering at the receiver output to the FPGA. The bit flip operates on a by-byte mode only. The low byte and high byte are flipped separately. The low byte is still transmitted first. This feature is used in conjunction with transmitter and word aligner bit flip in SONET mode. (2) For more information, refer to the Stratix GX Analog Description chapter. (3) SONET data rate is set at 2488.32 Mbps by default. Other data rates are possible, but they must adhere to the set multiplication factor of 2, 4, 5, 8, 10, 16, 20 of the input clock. Multiplication factors of 2, 4, 5 must use the refclkb pins. A multiplication factor of 2 also requires that the receiver PLL be trained by the transmitter PLL.
Altera Corporation 4–27 January 2005 Stratix GX Transceiver User Guide SONET Mode MegaWizard Plug-In Manager
Figure 4–21. MegaWizard Plug-In Manager - ALTGXB (Page 7 of 9) - Receiver (3) Notes (1)–(7)
Notes to Figure 4–21: (1) Indicates to the word aligner to either align to an A1A2 or A1A1A2A2 pattern. Low = A1A2, High = A1A1A2A2. (2) For more information, refer to the Stratix GX Analog Description chapter. (3) Transmitter PLL and receiver PLL lock indicator. For pll_locked, High = transmitter PLL locked to reference clock. For rx_locked, Low = receiver PLL locked to reference clock. (4) Receiver recovered clock output. There is one recovered clock available per receiver channel. (5) Indicates when the word aligner has aligned to the byte boundary. The rx_syncstatus signal goes high for one rx_clkout period when the word aligner aligns to the new byte boundary. In 16-bit mode, each high and low byte has a separate rx_syncstatus signal. (6) Rx_patterndetect is similar to rx_syncstatus, with the exception that the rx_patterndetect asserts only when the word alignment pattern appears in the data stream within the synchronized byte boundary. (7) The rx_a1a2sizeout is a loopback of the rx_a1a2size signal that is synchronized with the current byte from the word aligner.
4–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 SONET Mode
Figure 4–22. MegaWizard Plug-In Manager - ALTGXB (Page 8 of 9) - Transmitter Notes (1), (2)
Notes to Figure 4–22: (1) Flips the bit ordering from the FPGA to the transmitter input. Bit-flip operates on a by-byte mode only. The low byte and high byte are flipped separately. The low byte is still transmitted first. This feature is used in conjunction with receiver and word aligner bit-flip in SONET mode. (2) For more information, refer to the Stratix GX Analog Description chapter.
Altera Corporation 4–29 January 2005 Stratix GX Transceiver User Guide SONET Mode MegaWizard Plug-In Manager
Figure 4–23. MegaWizard Plug-In Manager - ALTGXB (Page 9 of 9) - Summary
4–30 Altera Corporation Stratix GX Transceiver User Guide January 2005 5. XAUI Mode
Introduction The 10 Gigabit Attachment Unit Interface (XAUI) is an optional, self-managed interface that can be inserted between the reconciliation sublayer and the PHY layer to transparently extend the physical reach of the 10 Gigabit Media Independent Interface (XGMII).
XAUI addresses several physical limitations of the XGMII. XGMII signaling is based on the HSTL class 1 single-ended I/O standard, which has an electrical distance limitation of approximately 7 cm. Because XAUI uses low voltage differential signaling method, the electrical limitation is increased to approximately 50 cm. Another advantage of XAUI is simplification of backplane and board trace routing. XGMII is composed of 32 transmit channels, 32 receive channels, 1 transmit clock, 1 receive clock, 4 transmitter control characters, and 4 receive control characters for a 74-pin wide interface in total. XAUI, on the other hand, only consists of 4 differential transmitter channels and 4 differential receiver channels for a 16-pin wide interface in total. This reduction in pin count significantly simplifies the routing process in the layout design. Figure 5–1 shows the relationships between the XGMII and XAUI layers.
Stratix® GX devices offer the following XAUI features:
■ Serial data rate range from 500 Mbps to 3.1875 Gbps ■ Input reference clock range from 25 to 637.5 MHz ■ Parallel interface width of 16 bits ■ 8B/10B encoder and decoder ■ Word aligner supports 10-bit code-group ■ Channel deskew ■ Rate compensation or elastic buffer ■ XGMII-to -PCS code conversion on transmit ■ PCS-to -XGMII code conversion on receive ■ Byte deserializer
Altera Corporation 5–1 January 2005 Introduction
Figure 5–1. XGMII & XAUI Relationship to ISO/IEC Open Systems Interconnection (OSI) Reference Model & IEEE 802.3 CSMA/CD LAN Model
LAN Carrier Sense Multiple Access/Collision Detect (CSMA/CD) OSI Reference Layers Model Layers Higher Layers
Application Logical Link Control (LLC)
Presentation MAC Control (optional) Session Media Access Control (MAC)
Transport Reconciliation
Network 10 Gigabit Media Independent Interface XGMII Extender Sublayer Data Link Optional XGMII 10 Gigabit Attachment Unit Interface Extender Physical XGMII Extender Sublayer 10 Gigabit Media Independent Interface Physical Coding Sublayer Physical Medium Attachment Physical Layer Device Physical Medium Dependent Medium Dependent Interface Medium
10 Gb/s
As noted earlier, the XGMII interface consists of 4 lanes of 8 bits. At the transmit side of the XAUI interface, the data and control characters are converted within the XGXS into an 8B/10B encoded data stream. Each data stream is then transmitted across a single differential pair running at 3.125 Gbps. At the XAUI receiver, the incoming data is decoded and mapped back to the 32 bit XGMII format. This process provides a transparent extension of the physical reach of the XGMII and also reduces the interface pin count.
5–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
XAUI functions as a self-managed interface because code-group synchronization, channel deskew, and clock domain decoupling are handled with no upper layer support requirements. These features are accomplished based on Physical Coding Sublayer (PCS) code-groups that are used during the Inter-Packet Gap (IPG) time and during idle periods. PCS code-groups are mapped by the XGMII Extender Sublayer (XGXS) to XGMII characters, as specified in Table 5–1.
Table 5–1. XGMII Character to PCS Code-Group Mapping Note (1)
XGMII TXC XGMII TXD PCD Code-Group Description 0 00 through FF Dxx,y Normal data transmission 1 07 K28.0 or K28.3 or Idle in ||I|| K28.5 1 07 K28.5 Idle in ||T|| 1 9C K28.4 Sequence 1 FB K27.7 Start 1 FD K29.7 Terminate 1 FE K30.7 Error 1 Reserved XGMII character 1 Any other value K30.7 Invalid XGMII character
Note to Table 5–1: (1) Values in TXD column are in hexadecimal.
Figure 5–2 shows an example of the mapping between XGMII characters to the PCS code-groups used in XAUI. The idle characters are mapped to a pseudorandom sequence of ||A||, ||R||, and ||K|| code-groups.
Altera Corporation 5–3 January 2005 Stratix GX Transceiver User Guide Introduction
Figure 5–2. Example of Mapping XGMII Characters to PCS Code-Groups
XGMII
T/RXD<7..0> I I S Dp DDD --- D D DD I I I I I I
T/RXD<15..8> ITI DpDp D D D --- D DD I I I I I I
T/RXD<23..16> I I Dp Dp D D D --- D D D I I I I I I I
T/RXD<31..24> I I Dp Ds DDD --- D D D I I I I I I I
PCS Lane 0 KRSDDp D D D --- D D D A R R K K R
Lane 1 K R Dp Dp D D D --- D D D T A R R K K R
Lane 2 K R Dp Dp D D D --- D D D K A R R K K R
Lane 3 K RDsDp D D D --- D D D K A R R K K R
The PCS code-groups are sent via PCS ordered sets. PCS ordered sets consist of combinations of special and data code-groups defined as a column of code-groups. These ordered sets are composed of four code- groups beginning in lane 0. Table 5–2 lists the defined idle ordered sets (||I||) that are used for the self managed properties of XAUI.
Table 5–2. Defined Idle Ordered Set
Number of Code Ordered_Set Encoding Code_Groups ||I| Idle Substitute for XGMII Idle ||K|| Sync column 4 /K28.5/K28.5/K28.5/K28.5/ ||R|| Skip column 4 /K28.0/K28.0/K28.0/K28.0/ ||A|| Align column 4 /K28.3/K28.3/K28.3/K28.3/
This section briefly introduces XAUI, along with the code-groups and ordered sets associated with this self-managed interface. For full details on the XAUI standard, refer to clauses 47–48 in the 10 Gigabit Ethernet standard (IEEE 802.3ae).
XAUI mode enables the configuring of transceiver blocks to support XAUI synchronization, channel alignment, rate compensation, XGMII to PCS code-group conversion, and PCS code-group-to-XGMII conversion. This section describes the supported digital architecture, clocking schemes, and software implementation of the XAUI mode. Figure 5–3 shows a block diagram of a duplex channel configured in XAUI mode.
5–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–3. Block Diagram of a Duplex Channel Configured in XAUI Mode
Analog Section Digital Section
Deserializer Word Aligner
Clock Channel Recovery Unit Aligner Rate Phase Matcher 8B/10B Byte Compensation Decoder Serializer FIFO Buffer Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Phase 8B/10B Byte Compensation Serializer Encoder Serializer FIFO Buffer
Receiver Transmitter
XAUI Mode Figure 5–4 diagrams the digital components of the receiver in XAUI Receiver mode. Architecture
Figure 5–4. Block diagram of Receiver Digital Components in XAUI Mode
Analog Section Digital Section
Deserializer Word Aligner
Clock Channel Recovery Unit Aligner Rate Phase Compensation Matcher 8B/10B Byte FIFO Buffer Decoder Serializer Reference Receiver Clock PLL
Receiver
Altera Corporation 5–5 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
Word Aligner
For embedded clocking schemes, the clock is recovered from the incoming data stream based on the transition density of the data. This feature eliminates the need for you to factor in receiver skew margins between the clock and data. However, with this clocking methodology, the word boundary of the re-timed data can be altered. Stratix GX transceivers offer an embedded word alignment circuit that can be used in conjunction with the pattern detector to align the word boundary of the re-timed data to a specified comma. You can configure this embedded circuit to synchronize with the XAUI protocols.
The word aligner is composed of a pattern detector and synchronization state machines. The word aligner cannot be bypassed, but if the rx_enacdet signal is not used, the word aligner does not alter the data. Figure 5–5 shows the various components of the word aligner. The functionality of each component is described in the following sections.
Figure 5–5. Stratix GX Word Aligner Components
WORD ALIGNER
PATTERN SYNCHRONIZATION DETECTOR STATE MACHINES
10-BIT XAUI MODE MODE
Pattern Detector Module The pattern detector matches a pre-defined comma to the current byte boundary. If the comma is found, the optional rx_patterndetect signal is asserted for the duration of one clock cycle to signify that the comma exists in the current word boundary. The pattern detector module indicates only that the signal exists and does not modify the word boundary. Modification of the word boundary is discussed in the word alignment and synchronization sections. You can program a 10-bit pattern for the pattern detector to recognize.
5–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
This module matches the 10-bit comma specified in the MegaWizard® Plug-In Manager with the data and its complement in the current word boundary. Both positive and negative disparities are checked in this mode. For example, if a /K28.5/ (b'0011111010) pattern is specified as the comma, the rx_patterndetect signal is asserted if b'0011111010 or b'1100000101 is detected in the incoming data.
XAUI uses an embedded clocking scheme that re-times the data, which can also alter the code-group boundary. The boundaries of the code-groups are realigned through a synchronization process specified in clause 48 of the IEEE 802.3ae standard, which states that synchronization is achieved upon the reception of four /K28.5/ commas. Each comma can be followed by any number of valid code-groups. Invalid code-groups are not supported during the synchronization stage.
XAUI Synchronization Mode When a Stratix GX transceiver is configured to the XAUI protocol, the built-in pattern detector, word aligner, and XAUI state machines adhere to the PCS synchronization specification. The code-group synchronization is achieved upon the reception of four /K28.5/ commas. Each comma is followed by any number of valid code-groups. Invalid code-groups are not supported during the synchronization stage. When code-group synchronization is achieved, the optional rx_syncstatus[] signal is asserted. Refer to clause 47-48 of the IEEE P802.3ae standard for more information regarding the operation of the synchronization phase. If the rx_sigdet signal is valid and the reset is deasserted, the synchronization state machine begins the synchronization process. If either of the two signals are not valid, the state machine falls out of the synchronization process and waits for the valid rx_sigdet signal and reset.
For reference, the PCS synchronization state diagram specified in clause 48 of the IEEE P802.3ae is shown in Figure 5–6.
Altera Corporation 5–7 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
Figure 5–6. IEEE 802.3ae PCS Synchronization State Diagram
Note to Figure 5–6: (1) lane_sync_status
5–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Channel Aligner
You use the channel aligner when implementing the XAUI protocol, to ensure that the channels are aligned. The channel aligner uses a 16-word- deep FIFO module.
Ordered sets can be misaligned with respect to one another because of board skew or differences between the independent clock recoveries per serial lane. Channel alignment re-aligns the ordered sets. This process is commonly referred to as deskew or channel bonding. Channel alignment is accomplished by using the alignment code-group, referred to as /A/. The /A/ code-group is transmitted simultaneously on all four lanes, constituting an ||A|| ordered set, during idles or inter packet gaps (IPG). XAUI receivers use these code-groups to resolve any lane to lane skew. Skew between the lanes can be up to 40 UI (12.8ns) as specified in the standard, which relaxes the board design constraints. Figure 5–7 shows lane skew at the receiver input, and how the deskew circuitry uses the /A/ code-group to deskew the channels.
Figure 5–7. Example of Lane Skew at Receiver Input
Lane 0 KRKKKRKKA R R R
Lane 1 KRKKKRKKA R R R
Lane 2 KRKKKRKKA R R R
Lane 3 KRKKKRKKA R R R
Lane 0 KRKKKRKKA R R R
Lane 1 KRKKKRKKA R R R
Lane 2 KRKKKRKKA R R R
Lane 3 KRKKKRKKA R R R
Altera Corporation 5–9 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
Figure 5–8. IEEE802.3ae PCS Deskew State Diagram
5–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Stratix GX transceivers handle XAUI channel alignment with a dedicated deskew macro consisting of a 16-word-deep FIFO module that is controlled by a XAUI deskew state machine. The XAUI deskew state machine first looks for the /A/ code-group within each channel. When /A/ is detected in each channel, the deskew FIFO module is enabled. The deskew state machine then monitors the reception of /A/ code-groups. When four aligned /A/ code-groups are received, the rx_channelaligned[] signal is asserted. The deskew state machine continues to monitor the reception of /A/ code-groups and deasserts the rx_channelaligned[] signal if alignment conditions are lost. This built-in deskew macro is only enabled for the XAUI protocol. For reference, the PCS deskew state diagram specified in clause 48 of the IEEE P802.3ae is shown in Figure 5–8.
Rate Matcher
XAUI can operate in multi-crystal environments, which can tolerate a frequency variation of ±100 ppm between crystals. Stratix GX transceivers have embedded circuitry to perform clock rate compensation. This is achieved by the insertion or removal of the PCS SKIP code-group (/R/) from the inter packet gap (IPG) or idle stream. This process is called rate matching and is sometimes referred to as clock rate compensation.
The rate matcher in Stratix GX transceivers consists of a 12-word-deep FIFO module along with control logic. In XAUI mode, the controller begins to write data into the FIFO module whenever the rx_channelaligned signal is asserted. Within the control logic, there is a FIFO module counter that keeps track of the read and write executions. When the FIFO module is near an overflow condition, the receivers delete the /R/ code-group simultaneously across all channels during IPG or idle conditions. If the FIFO counter is near an underflow condition, the receivers insert the /R/ code-group simultaneously across all channels during IPG or idle conditions. This circuitry compensates for ±100 ppm frequency variations.
8B/10B Decoder
The 8B/10B decoder is part of the Stratix GX transceiver blocks. The purpose of the 8B/10B decoder is to restore the 8-bit data + 1-bit control identifier from the 10-bit code.
Altera Corporation 5–11 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
10-Bit Decoding The 8B/10B decoder translates the 10-bit encode code into the 8-bit equivalent data or control code. The 10-bit encoded code is received LSB to MSB. The data that is received must be from the supported Dx.y or Kx.y list. All 8B/10B control signals (disparity error, control detect, and code error) are pipelined with the data in the Stratix GX receiver block and are edge-aligned with the data. Figure 5–9 diagrams the 10- to 8-bit conversion.
Figure 5–9. 10-Bit to 8-Bit Conversion
jhgf iedcba
9 8 7 6 5 4 3 2 1 0
MSB received LSB received last first
8b-10b conversion
7 6 5 4 3 2 1 0 Parallel Data + CTRL
HGFEDCBA
Reset The rxdigitalreset signal governs the reset condition of the 8B/10B decoder. In reset, the disparity registers are cleared. Upon exiting reset, the 8B/10B decoder can start with either a positive or negative disparity. The decoder calculates the initial running disparity based on the first valid code received.
The receiver block must be word-aligned after reset before the 8B/10B decoder can decode valid data or control codes.
Code Error Detect The rx_errdetect signal indicates when the code received contains an error. This port is optional and if not in use, there is no way to detect whether a code received is valid or not. The rx_errdetect goes high if code that is received is invalid or if it contains a disparity error. If code that is received is not part of the valid Dx.y or Kx.y list, the rx_errdetect signal goes high. This signal is aligned to the invalid code word that is received at the FPGA logic array.
5–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Disparity Error Detector The 8B/10B decoder detects disparity errors based on which 10-bit code it received. The disparity error is indicated at the optional rx_disperr port. The current running disparity is based on the disparity calculation of the last code received. The disparity calculation is described in Appendix A, Data & Control Codes.
If negative disparity is calculated for the last 10-bit code, a neutral or positive disparity 10-bit code is expected. If the decoder does not receive a neutral or positive disparity 10-bit code, the rx_disperr signal goes high, which indicates that the code received had a disparity error.
If a positive disparity is calculated, a neutral or negative disparity 10-bit code is expected. Rx_disperr goes high if the code received is not as expected. When the rx_disperr signal is high, the rx_errdetect signal also transitions high.
Figure 5–10 shows a case where the disparity is violated. A K28.5 code has an 8-bit value of 8'hbc and a 10-bit value (jhgfiedcba). The 10-bit value is 10'b0011111010 (10'h17c) for RD- or 10'b1100000101 (10'h283) for RD+. Assume that the running disparity at time n-1 is negative, so the expected code at time n is from the RD- column. Since a K28.5 does not have a balanced 10-bit code (equal number of 1’s and 0’s), the expected RD code toggles back and forth between RD- and RD+. At time n+3, the 8B/10B decoder received a RD+ K28.5 code (10'h283), which makes the current running disparity negative. At time n+4, because the current disparity is negative, a K28.5 from the RD- column is expected, but a K28.5 code from the RD+ is received instead. This code prompts rx_disperr to go high during time n+4 to indicate that the K28.5 code had a disparity error. The current running disparity at the end of time n+4 is negative, because a K28.5 from the RD+ column was received. Based on the current running disparity at the end of time n+5, a positive disparity K28.5 code (from the RD-) column is expected at time n+5.
Altera Corporation 5–13 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
Figure 5–10. Disparity Error
n n+1 n+2 n+3 n+4 n+5 n+6 n+7
clock
rx_out[7:0 ] 07 07 07 07FE 07 07 07
rx_disperr
rx_errdetect
rx_ctrldetect
Expected RD code RD- RD+RD- RD+ RD- RD- RD+ RD-
RD code received RD- RD+RD- RD+ RD+ RD- RD+ RD-
rx_in 17C 283 17C 283 28317C 283 17C
Control Detect The 8B/10B has the ability to differentiate between data and control codes via the rx_ctrldetect port. If this port is not in use, there is no way to differentiate Dx.y from Kx.y.
Figure 5–11 shows an example waveform demonstrating the detection of a K28.5 code (BC + ctrl). The rx_ctrldetect=1'b1 is aligned with 8'hbc, which indicates that this code is a control code. The reset of the code received is data.
Figure 5–11. Control Code Detection
clock
rx_out[7:0] 83 78 BC 07 0F 00 BF 3C
rx_ctrldetect
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
5–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
PCS - XGMII Code Conversion
In XAUI mode, the 8b/10b decoder in Stratix GX transceivers is controlled by a global receiver state machine that maps various PCS code-groups into specific 8-bit XGMII codes. Table 5–3 lists the PCS code group to XGMII character mapping.
Table 5–3. PCS Code-Group to XGMII Character Mapping Note (1)
XGMII RXC XGMII RXD PCS Code Group Description 0 00 through FF Dxx.y Normal data reception 1 07 K28.0 or K28.3 or Idle in ||I|| K28.5 1 07 K28.5 Idle in ||T|| 1 9C K28.4 Sequence 1 FB K27.7 Start 1 FD K29.7 Terminate 1 FE K30.7 Error 1 FE Invalid code-group Received code- group
Note to Table 5–3: (1) Values in RXD column are in hexadecimal.
Byte Deserializer
The byte deserializer module reduces the speed at which the FPGA logic array must run to meet performance specifications. It is possible to bring the data rate down from the line rate by a factor of 20.
The input to this module is 8 bits of data; the output to the FPGA logic array is deserialized to 16 bits. The byte deserializer does not process the data, and therefore, the control signals fed to the module are simply processed to match the latency to the data.
The byte deserializer in the receiver block takes in up to 13 bits. It is possible to feed the following to the byte deserialzer:
■ 8 bits of data and up to 2 control signals (rx_patterndetect, rx_syncstatus) ■ 8 bits of data and up to 5 control signals (rx_patterndetect, rx_syncstatus, rx_disperr, rx_ctrldetect, and rx_errdetect)
Altera Corporation 5–15 January 2005 Stratix GX Transceiver User Guide XAUI Mode Receiver Architecture
The byte deserializer outputs up to 26 bits, depending on the number of bits that was passed to it. When the input includes data and control signals, the data and the control signals are deserialized to include double the data bits and 2 bits of each control signal, one for the MSB and one for the LSB. This case is shown in the XAUI mode where the inputs to the Byte Deserializer are datain[7..0], patterndetect, syncstatus, disperr, ctrldet, and errdet. These 13 input signals feeding the byte deserializer and 26 output signals are fed to the FPGA logic array. The signals are sent into the logic array as two 13-bit buses. The aggregate bandwidth does not change by using the byte deserializer because the logic array data width is doubled.
Figure 5–12 demonstrates input and output signals of the byte deserializer when deserializing an 8-bit data input to 16 bits. In this case, the alignment pattern A (10111100) is located in the MSB of the 16-bit output, and this is reflected with patterndetect[1] going high. The output of the byte deserializer is BA, DC, FE, and so on.
Figure 5–12. Receiver Byte Deserializer in 8/16-Bit Mode with Alignment Pattern in MSB
inclk A BCDEF xxxxxxxxxx 1010100000 1100011000 1111000111 1010101010 1100110011 data_in[7..0] BA DC xxxxxxxxxxxxxxxxxxxx 1010100000xxxxxxxxxx 11110001111100011000 data_out[15..0]
patterndetect[0]
patterndetect[1]
Figure 5–13 demonstrates the alternate case of the alignment pattern found in the LSB of the 16-bit output. Correspondingly, patterndetect[0] goes high. In this case, the output is BA, DC, FE, and so on.
5–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–13. Receiver Byte Deserializer in 8/16-Bit Mode With Alignment Pattern in LSB
inclk A BCDEF
10111100 11000110 11110001 10101010 11001100 11111000 data_in[7..0] BA DC
xxxxxxxx01101111 1100011010111100 10101010 11110001 data_out[15..0]
patterndetect[0]
patterndetect[1]
The logic array must include logic to perform byte position alignment when the data enters the logic array, as seen in Figure 5–14. In this example, the byte position selection logic determines the proper byte position based on the pattern detect signal.
Figure 5–14. Receiver Byte Deserializer Data Recovery in Logic Array
Gigabit Transceiver Block Logic Array
rx_out[17..10] rx_out_post[17..10] DQ 8 8 rx_out_post[17..0] 8 rx_out_align[17..0] Phase 8 Compensation 16 FIFO Buffer {rx_out[7..0], rx_out_post[17..10]}
rx_out[7..0] rx_out_post[7..0] DQ 8 8
Byte Boundary Selection Logic
Altera Corporation 5–17 January 2005 Stratix GX Transceiver User Guide XAUI Mode Transmitter Architecture
Receiver Phase Compensation FIFO Module
The receiver phase compensation FIFO module is located at the FPGA logic array interface in the receiver block and is four words deep. The FIFO module compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
In XAUI mode, the write port is clocked by the refclk from the transmitter PLL. This clock is half the rate if the byte deserializer is used. The read clock is clocked by coreclk (output from the transmitter PLL).
The receiver phase compensation FIFO module only accounts for phase differences.
The receiver phase compensation FIFO module is always used and cannot be bypassed.
XAUI Mode Figure 5–15 diagrams the transmitter digital components in XAUI mode. Transmitter Architecture
Figure 5–15. Block Diagram of Transmitter Digital Components in XAUI Mode
Analog Section Digital Section
Reference Transmitter Clock PLL
Phase 8B/10B Byte Compensation Serializer Encoder Serializer FIFO Buffer
Transmitter
Transmitter Phase Compensation FIFO Module
The Transmitter Phase Compensation FIFO module is located at the FPGA logic array interface in the transmitter block and is four words deep. The FIFO module compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
The read port of the phase compensation FIFO module is clocked by the transmitter PLL clock. The write clock is clocked by tx_coreclk. You can select the tx_coreclk as an optional transmitter input port to
5–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
receive a clock supply. In this case, there must be no frequency difference between the tx_coreclk and the transmitter PLL clock. The transmitter Phase Compensation FIFO module can only account for phase differences.
If the tx_coreclk is not selected as an optional input transmitter port, tx_coreclk is fed by coreclk_out. This connection occurs using the logic array routing. As such, the software defaults to using an FPGA global clock, regional clock, or fast regional clock resource.
The transmitter phase compensation FIFO module is always used and cannot be bypassed. The input to this FIFO module is the data from the FPGA logic array. If they are used, the tx_ctrlenable and tx_forcedisparity signals are also passed through the FIFO module to ensure that they are synchronized with the data when they feed to the subsequent module.
Byte Serializer
The byte serializer in the transmitter block takes a 16-bit input from the FPGA logic array and serializes it to 8 bits. It transmits from the least significant byte to the most significant byte. The transmitter digital reset must always be used to reset the FIFO module pointers whenever an unknown state is encountered, such as when the transmitter PLL loses lock. Refer to the chapter Reset Control & Power Down for further details on the reset sequence.
Figure 5–16 demonstrates input and output signals of the byte serializer when serializing a 20-bit input to 10 bits. The tx_in[] signal is the input that has already passed from the FPGA logic array through the transmitter phase compensation FIFO module.
Figure 5–16. Transmitter Byte Serializer in 16- to 8-Bit Mode
D1 D2 D3
0001010001101111 1100011011110001 1010101010110011 datain[15:0]
D1 LSB D1 MSB D2 LSB D2 MSB xxxxxxxx xxxxxxxx 01101111 00010100 11110001 11000110 dataout[7:0]
The LSB is transmitted before the MSB in the transmitter byte serializer. Figure 5–16 shows the order of data transmitted. For the input of D1, the output is D1LSB and then D1MSB.
Altera Corporation 5–19 January 2005 Stratix GX Transceiver User Guide XAUI Mode Transmitter Architecture
XGMII Character to PCS Code-Group Mapping
In XAUI mode, the 8b/10b encoder in the Stratix GX transceiver is controlled by a global transmitter state machine that maps various 8-bit XGMII codes to 10-bit PCS code-groups. This state machine complies with the IEEE 802.3ae PCS transmit specification. For reference, the PCS transmit source state diagram, specified in clause 48 of the IEEE P802.3ae specification, is shown in Figure 5–17.
Figure 5–17. IEEE 802.3ae PCS Transmit Source State Diagram
!reset * !(TX=||IDLE|| + TX=||Q||)
SEND_DATA IF TX=||T|| THEN cvtx_terminate tx_code-group<39:0> ENCODE(TX) PUDR reset (next_ifg=K + A_CNT 0) next_ifg=A * A_CNT=0
SEND_K SEND_A tx_code-group<39:0> ||K|| tx_code-group<39:0> ||A|| next_ifg A next_ifg K PUDR PUDR UCT
Q_det !Q_det
SEND_Q tx_code-group(39:0> TQMSG Q_det false PUDR
UCT A_CNT 0 * code_sel=1 A_CNT 0 * SEND_RANDOM_R A_CNT 0 * code_sel=0 SEND_RANDOM_K code_sel=1 tx_code-group<39:0> ||R|| tx_code-group<39:0> ||K|| PUDR PUDR A_CNT 0 * code_sel=0
A_CNT=0 A_CNT=0
SEND_RANDOM_A tx_code-group<39:0> ||A|| PUDR !Q_det * code_sel=1 Q_det !Q_det * code_sel=0
SEND_RANDOM_Q tx_code-group<39:0> TQMSG Q_det false PUDR
code_sel=0 code_sel=1
5–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Table 5–4 lists the XGMII character-to -PCS code-group mapping.
Table 5–4. XGMII Character to PCS Code-Group Mapping Note (1)
XGMII XGMII TXD PCS Code-Group Description 0 00 though FF Dxx,y Normal data transmission 1 07 K28.0 or K28.3 or Idle in ||I|| K28.5 1 07 K28.5 Idle in ||T|| 1 9C K28.4 Sequence 1 FB K27.7 Start 1 FD K29.7 Terminate 1 FE K30.7 Error 1 Any other value K30.7 Invalid XGMII character
Note to Table 5–4: (1) Values in TXD column are in hexadecimal.
8B/10B Encoder
The 8B/10B encoder is part of the Stratix GX transceiver blocks. The purpose of the 8B/10B encoder is to translate 8-bit data and a 1-bit control identifier (via tx_ctrlenable) into a 10-bit DC balanced data stream.
For additional information about the 8B/10B code itself, refer to “8B/10B Code” on page 10–1. The 8B/10B encoder translates the 8-bit data or 8-bit control character to its 10-bit equivalent. The conversion format is shown in Figure 5–18. The10-bit resultant data is transmitted LSB first by the serializer.
Altera Corporation 5–21 January 2005 Stratix GX Transceiver User Guide XAUI Mode Transmitter Architecture
Figure 5–18. 8B/10B Conversion Format
7 6 5 4 3 2 1 0 + CTRL
HGFEDCBA
8b-10b conversion
jhgf iedcba
9 8 7 6 5 4 3 2 1 0
MSB sent last LSB sent first
8B/10B Reset Condition The txdigitalreset controls the reset of the 8B/10B encoder. To reset the 8B/10B encoder, txdigitalreset must be high. During reset, the running disparity registers are cleared, along with the data registers. Also, the 8B/10B encoder outputs a K28.5 pattern from the RD- column continuously until txdigitalreset goes low. The tx_in[] and tx_ctrlenable[] are ignored during the reset state. Once out of reset, the 8B/10B encoder starts with a bias towards negative disparity (RD-) and transmits three K28.5 codes for synchronizing before it starts encoding and transmitting the data on tx_in[].
If the reset for the 8B/10B encoder is asserted, the 8B/10B decoder receiving the data may receive an invalid code error, sync error, control detect, and/or disparity error while txdigitalreset is high.
Figure 5–19 shows the reset behavior of the 8B/10B encoder. When in reset (txdigitalreset is high) a K28.5- (K28.5 10-bit code from the RD- column) is sent continuously until txdigitalreset goes low. Because of pipelining of the transmitter channel, there are several don’t-care values (10'hxxx) until the first of three K28.5 is sent (Figure 5–19 shows three don’t-cares). Normal user data follows the third K28.5.
5–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–19. Transmitter Output During Reset Conditions
clock
txdigitalreset
(1) tx_out[9:0 ] K28.5- K28.5- K28.5- xxx xxx xxx K28.5- k28.5+ K28.5- Dx.y+
Note to Figure 5–19: (1) K28.5 is an example, but an 07 control generates an idle sequence based on the 802.3 specification.
Control Code Encoding The tx_ctrlenable[] signal dictates when a control code is to be inserted in the encoded data flow. When tx_ctrlenable[] is low, the byte at tx_in[] is encoded as data. When tx_ctrlenable[] is high, tx_in[] is encoded as a control word. The waveform in Figure 5–20 shows that 0x07 is encoded as a control code. The other values of tx_in[] are encoded as data.
Figure 5–20. Control Word Identification Waveform
clock
tx_in[7:0] 83 78 BC 07 0F 00 BF 3C
tx_ctrlenable
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
The 8B/10B encoder does not check to see if the code word that is entered is one of the 12 valid codes. If an invalid control code is entered, the resulting 10-bit code might be encoded as an invalid code, which does not map to a valid Dx.y or Kx.y code), or a valid Dx.y code, depending on the value entered.
Altera Corporation 5–23 January 2005 Stratix GX Transceiver User Guide XAUI Mode Clocking
An example is the invalid encoding of a K24.1 (data = 8'h38 + tx_ctrlenable = 1'b1). Depending on the current running disparity, you can encode the K24.1 to be 10'b0110001100 (0x18C), which is equivalent to a D24.6+ (0xD8 from the RD+ column). An 8B/10B decoder decodes this value incorrectly (based on the 8B/10B Fibre Channel specification).
XAUI Mode This section describes the clocking supported by the Stratix GX device in Clocking XAUI mode. XAUI Mode Channel Clocking
This section describes clocking of the transceiver, internal clocking details, and external clock ports in XAUI mode. Each block diagram shows the input and output port clocks. Most of the settings are based on per transceiver block (4 channels) basis. By default, the MegaWizard Plug-In Manager selects a set of clocks for transmitters and receivers in a transceiver block when XAUI mode is selected. The MegaWizard Plug-In Manager also offers clock options other than the default selection, which facilitates the clocking scheme.
Figure 5–21 shows that the altgxb megafunction is configured such that the train receiver PLL with transmitter PLL is enabled. The transmitter PLL is fed from an inclk port that can itself be fed from a dedicated REFCLKB, global clock, regional clock, or fast regional clock source. The receiver logic is clocked by the recovered clock from the clock recovery unit up to a deskew FIFO module in the data path. Rate matching is done between recovered clock of channel 0 and refclk from the transmitter PLL. The data from the receive parallel interface, which is also from the phase compensation FIFO module, is clocked by coreclk_out from the transmitter PLL. On the transmitter channel, the output of the transmitter PLL, coreclk_out, is sent out of the logic array as an output and also loops back to clock the write side of the transmit phase compensation FIFO module and the read side of the receive phase compensation FIFO module.
5–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–21. Default Configuration of altgxb Megafunction in XAUI Mode
You can disable the train receiver PLL CRU clock from transmitter PLL feature in the altgxb MegaWizard Plug-In. Deselecting this option enables an additional rx_cruclk input reference clock port for the receiver PLL. You can use this feature to support additional multiplication factors for the receiver PLL, because it supports the separation of receiver and transmitter reference clocks. This separation is necessary if the output reference clock frequency from the transmitter PLL exceeds the 325 MHz phase frequency detector of the receiver PLL (see Chapter 2, Stratix GX Analog Description for more information). This configuration is shown in Figure 5–22.
f Refer to the Stratix GX FPGA Family data sheet for information on parallel interface speeds for other device speed grades.
Altera Corporation 5–25 January 2005 Stratix GX Transceiver User Guide XAUI Mode Clocking
Figure 5–22. Train Receiver PLL CRU Clock From Transmitter PLL Feature Is Disabled With Added Port RX_CRUCLK
If tx_coreclk is enabled, the train receiver CRU clock from transmitter PLL is disabled, and if other default options are also enabled, this configuration has an independent rx_cruclk that feeds the receiver PLL reference clock. This input clock port is only available when the receiver PLL is not trained by the transmitter PLL.
You can enable the write clock of the transmitter phase compensation FIFO module to manually feed in a clock from the FPGA logic array. You can use this option to optimize the global clock usage. For instance, if all transmitter channels between transceiver blocks are from a common clock domain, the transceiver instantiations use a total of one global resource instead of one global per transceiver block if the tx_coreclk option is not enabled. On the transmitter functionality screen under the optional port of transmitter section, if tx_coreclk is selected as an input port, the default clocking scheme changes by using tx_coreclk as the write clock for the phase compensation FIFO module.
There are two ways to connect tx_coreclk. To use coreclk_out, connect coreclk_out to tx_coreclk by using either gclk/rclk/fclk or logic array routing. Alternatively, tx_coreclk can be supplied from a crystal or any other clock source, as long as tx_coreclk is frequency-locked to the read side of the phase compensation FIFO module on the transmit side.
5–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
The tx_coreclk must be frequency matched with its respective read ports. The phase compensation FIFO module can only correct for phase, not for frequency differences. The receiver parallel interface clocks the data to the FPGA based on coreclk_out, which is the default option in the MegaWizard Plug-In Manager.
Figure 5–23 shows the clock configuration with these optional input ports enabled.
Figure 5–23. TX_CORECLK Enabled With RX_CRUCLK Port
Table 5–5 describes the input and output ports shown in Figure 5–23.
Table 5–5. List of Input & Output Ports Available in XAUI Mode
Clock Port Description inclk Input Input to the transmitter PLL. Available as a port when the transmitter PLL is instantiated. rx_cruclk Input Input to CRU. Available as a port when CRU is not trained by the transmitter PLL. tx_coreclk Input Clocks write port of the transmitter phase compensation FIFO module. Optional port in the Quartus® II software. Must be frequency matched to tx_pll_clk. If not available as a port, is fed by coreclk_out through logic array routing. coreclk_out Output Output clock from the transmitter PLL equivalent to tx_pll_clk. Available as port if the transmitter PLL is used.
Altera Corporation 5–27 January 2005 Stratix GX Transceiver User Guide XAUI Mode Clocking
XAUI Inter-Transceiver Block Clocking
This section describes guidelines for the transceiver interface clocking that is used inside the FPGA logic array when multiple transceiver blocks are active. The transceiver blocks for each mode are supported by transceiver-to-FPGA interface clocking, unique to the Stratix GX transceiver. Different input and output clocks are available based on the options provided by the Quartus II MegaWizard Plug-In Manager’s built-in functions. The number of supported channels varies based on the type of Stratix GX device you select (for example, EP1SGX40G, EP1SGX25F, and so on). Consider the clocking schemes at a system level with multiple lanes carefully to prevent pitfalls later in the design cycle. XAUI mode is transceiver-block-based and can only support lanes in multiples of four.
One of the clocking interfaces in the Stratix GX device is the interface between the transceiver and the FPGA, which can be further divided into FPGA-transmit of a transceiver and FPGA-receive of a transceiver. In XAUI mode, depending on the options set in the MegaWizard Plug-In Manager, you can use either the coreclk_out or tx_coreclk clock to send the data into the transmit of the transceiver. However, the tx_coreclk must be frequency locked with the transmit system clock of each transceiver block. (In each transceiver block, one transmitter PLL is shared among four transmitters.)
In a multi-transceiver block scenario, if there are synchronous data transfers based on transmit clocks when tx_coreclk is enabled for each channel, each enabled transceiver block must connect to one of the coreclk_out outputs. When tx_coreclk is not enabled, the Quartus II software automatically routes the coreclk_out signal to write the clock of the phase compensation FIFO module using a global, regional, or fast regional resource. In a multi-transceiver block configuration, this feature can lead to timing violations because the coreclk_out per transceiver block cannot guarantee a phase relationship. For this reason, Altera recommends clocking the tx_coreclk with a common clock for synchronous transmission.
In the multi-transceiver block case, use the transmit clock by enabling tx_coreclk and connecting one of the coreclk_out clock signals output from one of the transceiver blocks that is active. An illustration of this scheme is shown in Figure 5–24.
5–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–24. PLD to Transmit Interface Clocking Scheme in a Multi-Channel Application
ALTGXB (GX25f) PLD
coreclk_out[0]
Transceiver Block 0 tx_in_0[15..0]
tx_coreclk[0]
coreclk_out[1] tx_in_1[15..0] Transceiver Block 1 tx_coreclk[1] tx_coreclk[1]
PLD Transmit Data Clock Domain coreclk_out[2]
Transceiver Block 2 tx_in_2[15..0]
tx_coreclk[2]
coreclk_out[3] tx_in_3[15..0] Transceiver Block 3 tx_coreclk[3]
At the FPGA-receive interface, there is no receive parallel interface clock option in the MegaWizard Plug-In Manager; the default is the transmitter PLL output clock, which is a transceiver internal clock.
Altera recommends implementing channel bonding across the transceiver blocks used in Stratix GX devices to ensure that there is no skew between the transceiver blocks (if each transceiver is operating, no channel bonding is required and the data can simply go to destination registers, as shown in Figure 5–25). Also, all traces in your design should match.
Altera Corporation 5–29 January 2005 Stratix GX Transceiver User Guide XAUI Mode Clocking
Figure 5–25. Clocking Scheme in Multi-Channel, Only CORECLK_OUT Is Enabled
ALTGXB (GX25f) PLD
rx_out[15..0] Transceiver Block 0 coreclk_out[0]
Destination Register Logic FIFO Buffer
rx_out_1[15..0] FIFO Transceiver Block 1 Buffer coreclk_out[1]
FIFO Buffer
FIFO rx_out_2[15..0] Buffer
Transceiver Block 2 coreclk_out[2]
rx_out_3[15..0] Transceiver Block 3 coreclk_out[3] coreclk_out[3]
XAUI mode applications are typically transceiver block-based. The previous recommendations are valid in a multi-transceiver block situation. In a multi-transceiver block situation, data striping across the channels is common. Skew introduced between transceiver blocks by passive and active elements of the link must be de-skewed in the PLD core (channel alignment) to ensure error-free data.
5–30 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Another multi-transceiver block issue is the selection of the dedicated refclkb pin. Stratix GX channels are arranged in banks of four, which are called transceiver blocks. Each transceiver block has the ability to share a common reference clock through the Inter-Transceiver (IQ) lines. You can reduce the Stratix GX logic array clock usage by using the IQ lines. The IQ lines are used when a refclkb input port from one transceiver block or channel drives any other transceiver blocks or channels. The IQ line usage is determined automatically by the Quartus II software.
When determining the location of refclkb pins, consider what is fed by the pin you select. Table 5–6 shows the available IQ lines and which transceiver blocks are driven by refclkb. This information is based on the number of transceiver channels in the Stratix GX device.
Table 5–6. REFCLKB to Inter-Transceiver Line connections
REFCLKB in Channels in IQ Line Driven by Channel Density Transceiver Block Transceiver Block REFCLKB Number 8 channels 0 [3:0] IQ2 (EP1SGX10) 1 [7:4] IQ0 16 channels 0 [3:0] N/A (EP1SGX25) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 20 channels 0 [3:0] N/A (EP1SGX40) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 4 [19:16] N/A
Figure 5–26 shows the transceiver routing with respect to Inter- Transceiver lines. This information is vital when placing refclkb pins. (When placing refclkb pins, see Appendix C, REFCLKB Pin Constraints for information about analog reads and refclkb pin usage constraints.) For example, if a refclkb pin is required to feed a transmitter PLL using an IQ line, the refclkb pin cannot be in transceiver block 1, because IQ2 only feeds the receiver PLLs.
Altera Corporation 5–31 January 2005 Stratix GX Transceiver User Guide XAUI Mode Clocking
Figure 5–26. IQ Line Connections for EP1SGX25 Device
Transceiver Block 0
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 IQ0 IQ1 IQ2 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 1
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 2 16
PLD Global Clocks IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 3
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Figure 5–27 shows the transceiver routing with respect to IQ lines for the EP1SGX40G device. This device has an extra transceiver block (transceiver block 4), which is in the middle of the other transceiver blocks, as shown. It is important to use this information when placing refclkb pins. (When placing refclkb pins, see Appendix C, REFCLKB Pin Constraints for information about analog reads and refclkb pin usage constraints.)
5–32 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
For example, if a refclkb pin is required to feed a transmitter PLL using an IQ line, the refclkb pin cannot be in transceiver block 1, because IQ2 only feeds the receiver PLLs.
Figure 5–27. IQ Line Connections for EP1SGX40G
Transceiver Block 0
IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 1 IQ0 IQ1 IQ0 IQ1 IQ2 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 4 PLD
IQ0 Global IQ1 Global Clks, I/O Bus, Gen Routing TX PLL Clocks refclkb 16 /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
Transceiver Block 2 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 3 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
Altera Corporation 5–33 January 2005 Stratix GX Transceiver User Guide XAUI Mode MegaWizard Plug-In Manager
XAUI Mode This section describes the altgxb megafunction MegaWizard® Plug-In Manager options in XAUI mode. Altera recommends that the Stratix GX MegaWizard transceiver block be instantiated and parameterized through the Plug-In Manager MegaWizard Plug-In Manager in the Quartus II software. The Quartus II MegaWizard Plug-In Manager offers a graphical user interface (GUI) that organizes the altgxb options in easy-to-use sections. The MegaWizard Plug-In Manager also sets the proper ports and parameters automatically, based on the selected options and parameters. Invalid settings are automatically flagged to help prevent illegal configurations. The MegaWizard Plug-In Manager grays out any options that do not apply to XAUI mode.
Although it is possible to instantiate the Stratix GX block directly by calling out the altgxb megafunction, Altera recommends using the MegaWizard Plug-In Manager to instantiate the altgxb megafunction to reduce the chance of invalid settings.
XAUI Mode MegaWizard Considerations
Each altgxb MegaWizard instantiation can use one or more transceiver blocks based on the number of channels you select. There are four channels per transceiver block. In XAUI mode, the number of channels are in multiples of four or transceiver block based.
Each MegaWizard instantiation must have similar functionality and data rates. To use transceiver blocks that differ in functionality and/or data rates, create a separate MegaWizard instantiation for each transceiver block.
As mentioned in the clocking section, the MegaWizard Plug-In Manager displays the configuration of the altgxb megafunction. This diagram changes dynamically based on the selected mode, options, and clocking schemes.
XAUI Mode altgxb MegaWizard Options
Figures 5–28 through 5–33 show the MegaWizard Plug-In Manager pages where you select the options for a XAUI mode configuration.
5–34 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–28. MegaWizard Plug-In Manager - ALTGXB (Page 3 of 9) - General (1) Notes (1)–(7)
Notes to Figure 5–28: (1) Currently, only Stratix GX devices support the altgxb megafunction. (2) Select XAUI for XAUI protocol support. (3) XAUI protocol mode supports duplex only-operation mode. (4) You can select between 4 and the maximum number of channels available on the device in increments of 4. (5) 16 bits is double width. (6) For more information, refer to the Stratix GX Analog Description chapter. (7) The rxdigitalreset port resets the digital blocks in the receiver channel. Each active receiver channel has its own digital reset. The txdigitalreset port resets the digital blocks of the transmitter channel. Each active transmitter channel has its own digital reset. The rxanalogreset signal resets the receiver's analog circuits including the receiver PLL. Each active receiver channel has its own analog reset. The pll_areset port resets the entire transceiver block (all receiver and transmitter digital and analog circuits including receiver and transmitter PLLs). The pllenable port enables the entire transceiver block. If this signal goes low, the entire transceiver block is held in reset conditions.
Altera Corporation 5–35 January 2005 Stratix GX Transceiver User Guide XAUI Mode MegaWizard Plug-In Manager
Figure 5–29. MegaWizard Plug-In Manager - ALTGXB (Page 4 of 9) - General (2) Notes (1), (2)
Notes to Figure 5–29: (1) For more information, refer to the Loopback Modes chapter. (2) For more information, refer to the Stratix GX Built-In Self Test (BIST) chapter.
5–36 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–30. MegaWizard Plug-In Manager - ALTGXB (Page 5 of 9) - Receiver (1) Notes (1), (2)
Notes to Figure 5–30: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) Word aligner in XAUI mode is always set as a 10-bit K28.5 pattern. Both positive and negative disparities are checked.
Altera Corporation 5–37 January 2005 Stratix GX Transceiver User Guide XAUI Mode MegaWizard Plug-In Manager
Figure 5–31. MegaWizard Plug-In Manager - ALTGXB (Page 6 of 9) - Receiver (2) Notes (1)–(3)
Notes to Figure 5–31: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) For more information, refer to the Stratix GX Analog Description chapter. The Force Signal Detect option is always on and cannot be turned off. Because the signal detect circuitry is always forced, the rx_signaldetect is always set in XAUI mode. (3) XAUI Data Rate is set to 3125 Mbps by default. Other data rates are possible, but they must adhere to the set multiplication factor of 2,4,5,8,10,16,20 of the input clock. Multiplication factors of 2,4,5 must use the refclkb pins. Multiplication factor of 2 also requires that the receiver PLL be trained by the transmitter PLL.
5–38 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–32. MegaWizard Plug-In Manager - ALTGXB (Page 7 of 9) - Receiver (3) Notes (1)–(5)
Notes to Figure 5–32: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) Receiver PLL lock indicator. For rx_locked, Low = receiver PLL locked to reference clock. (3) rx_signaldetect is only available in XAUI mode. Because the signal detect circuitry is always forced, the rx_signaldetect signal is always set in XAUI and GIGE modes, supporting backward compatibility with existing designs. See the Stratix GX Analog Description chapter for additional information. (4) Indicates when the word aligner has aligned to the byte boundary. The rx_syncstatus signal goes high for one rx_clkout period when the word aligner aligns to the new byte boundary. If in 16-bit mode, each high and low byte has a separate rx_syncstatus signal. (5) rx_patterndetect is similar to the rx_syncstatus, except that rx_patterndetect asserts only when the word alignment pattern appears in the data stream within the synchronized byte boundary.
Altera Corporation 5–39 January 2005 Stratix GX Transceiver User Guide XAUI Mode MegaWizard Plug-In Manager
Figure 5–33. MegaWizard Plug-In Manager - ALTGXB (Page 8 of 9) - Transmitter Notes (1), (2)
Notes to Figure 5–33: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) tx_coreclk: You can optionally choose the write clock of the transmitter phase comp FIFO buffer. This clock should be frequency locked with the internal reference clock because the phase comp FIFO buffer cannot tolerate frequency variations and contains no error flags.
5–40 Altera Corporation Stratix GX Transceiver User Guide January 2005 XAUI Mode
Figure 5–34. MegaWizard Plug-In Manager - ALTGXB (Page 9 of 9) - Summary
Altera Corporation 5–41 January 2005 Stratix GX Transceiver User Guide XAUI Mode MegaWizard Plug-In Manager
5–42 Altera Corporation Stratix GX Transceiver User Guide January 2005 6. GigE Mode
Introduction The Gigabit Ethernet (GigE) mode in Stratix® GX devices supports a subset of the IEEE GigE standard. Stratix GX devices have Physical Coding Sub-layer (PCS) functions and Physical Medium Attachment (PMA) functions as Hard Intellectual Property (IP).
Stratix GX devices provide the following GigE features:
■ Serial data rate of 1.25 Gigabits per second ■ Input clock reference range of 62.5 to 625 MHz (these values are the minimum and maximum for an input reference clock with a data rate of 1.25 Gbps and an 8-bit data width) ■ Parallel interface width of 8 bits ■ 8B/10B encoding decoder ■ Word aligner supports 10-bit code groups ■ Rate compensation or elastic buffer ■ Gigabit Media Independent Interface (GMII) to PCS code conversion on transmit
The GMII is an intermediate or parallel interface that connects the PCS sub-layer with the media access control (MAC) in a system that supports GigE mode. The GigE physical layer is divided into three sub-layers: the PCS, the PMA, and the physical medium dependent (PMD) layers. If you implement a GMII-compliant interface, that interface offers data rates up to 1,000 Mbps at either half- or full-duplex modes.
The PCS provides synchronization, encoding, decoding, and rate matching services to the MAC. The PCS also provides autonegotiation to the network to negotiate speeds, carrier-detect signals, and collision-detect signals.
The PMA sublayer provides the PCS with a media-independent interface that a variety of serial physical media can connect to. This sublayer handles the serialization and deserialization of the data.
The PMD sublayer defines the physical attachments, such as connectors for different media types.
Figure 6–1 shows the positioning of these layers.
Altera Corporation 6–1 January 2005 Introduction
Figure 6–1. GMII Position Relative to OSI Reference Model
LAN CSMA/CD Layers
OSI Reference Model Layers Higher Layers
LLC - Logical Link Control Application MAC Control (Optional) Presentation MAC - Media Access Control Session Reconciliation
Transport GMII
Network PCS 1000BASE-X Data Link PHY PMA
Physical PMD
Medium
Stratix GX devices are used for the PCS and the PMA layers of the GigE physical layer. Stratix GX devices in GigE mode use built-in hard macros for the 8B/10B encoder/decoder, rate matcher, synchronizer, or the byte serializer/deserializer. Figure 6–2 shows these components. The rate matcher and the word aligner contain a dedicated state machine governing their functions, which is active only in GigE mode. GigE mode enables transceivers to support GMII-to-PCS code group conversion and idle generation. Table 6–1 shows the GigE code groups for the reference of idle ordered sets and configuration ordered sets, as explained in the “Idle Generation” section. For full details on the GigE standard and code- group functionality, refer to clause 36 in the Gigabit Ethernet standard (IEEE 802.3).
The remaining functions of the PCS—auto negotiation, collision detect, and carrier detect—must be implemented in user logic or external circuits if these functions are needed.
Table 6–1. GigE Code Groups (Part 1 of 2) Note (1)
Number of Code Ordered Set Encoding Code Groups /C/ Configuration Alternating /C1/ and /C2/ code groups /C1/ Configuration 1 4 /K28.5/D21.5/Config_Reg (1)
6–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Table 6–1. GigE Code Groups (Part 2 of 2) Note (1)
Number of Code Ordered Set Encoding Code Groups /C2/ Configuration 2 4 /K28.5/D2.2/Config_Reg (1) /I/ IDLE /I1/ is correcting; /I2/ is preserving /I1/ IDLE 1 2 /K28.5/D5.6/ /I2/ IDLE 2 2 /K28.5/D16.2/ Encapsulation /R/ Carrier_Extend 1 /K23.7/ /S/ Start_of_Packet 1 /K27.7/ /T/ End_of_Packet 1 /K29.7/ /V/ Error_Propagation 1 /K30.7/
Note to Table 6–1: (1) Two data code groups represent the Config_Reg value.
Figure 6–2. Block Diagram of a Duplex Channel Configured in GigE Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Reference Transmitter Clock PLL
Serializer Phase Byte 8B/10B Compensation Serializer Encoder FIFO Buffer
Receiver Transmitter
Altera Corporation 6–3 January 2005 Stratix GX Transceiver User Guide GigE Mode Receiver Architecture
GigE Mode Figure 6–3 shows the digital components of the Stratix GX receiver that Receiver are active in GigE mode. Architecture
Figure 6–3. Block Diagram of the Stratix GX Receiver Digital Components in GigE Mode
Analog Section Digital Section
Word Deserializer Aligner Phase Channel Rate Compensation Aligner 8B/10B Clock Matcher Byte FIFO Buffer Decoder Recovery Deserializer Unit
Reference Receiver Clock PLL
Receiver
The GigE mode receiver architecture includes:
■ Word aligner ■ Rate matcher ■ 8B/10B decoder ■ Receiver phase compensation FIFO buffer
Word Aligner
The word aligner is composed of a pattern detector and synchronization state machines. The word aligner cannot be bypassed, but if the application is not using the rx_enacdet signal, the word aligner does not alter the data. Figure 6–4 shows the various components of the word aligner. The “Pattern Detector Module” and “Synchronization State Machines” sections describe the functionality of the main components.
6–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–4. Components in Stratix GX Word Aligner
Word Aligner
Pattern Synchronization Detector State Machines
10-Bit GigE Mode Mode
For embedded clocking schemes, the clock is recovered from the incoming data stream based on the data transition density. Therefore, you do not need to factor in receiver skew margins between the clock and data. However, with this clocking methodology, the word boundary of the re-timed data might be altered. Stratix GX devices offer an embedded word alignment circuit that uses synchronization state machines in conjunction with the pattern detector to align the word boundary of the re-timed data to a specified comma. This embedded circuit can be configured to synchronize to the GigE protocols.
GigE mode requires synchronization to align the byte boundary of the receiver after incoming serial data is de-serialized. This step is necessary because the Stratix GX block uses a non-source-synchronous serial stream. To correctly align the byte boundary at the receiver, the Stratix GX device sends a unique synchronization pattern to the receiver that does not occur between any Dx.y or Kx.y code combinations, namely, a /K28.5/ 10-bit comma.
Pattern Detector Module The pattern detector matches a predefined comma to the current byte- boundary. If the comma is present, the optional rx_patterndetect signal asserts for one clock cycle to signify that the comma exists in the current word boundary. The pattern detector module only indicates that the signal exists and does not modify the word boundary. A 10-bit pattern can be programmed for the pattern detector to recognize.
Altera Corporation 6–5 January 2005 Stratix GX Transceiver User Guide GigE Mode Receiver Architecture
In GigE mode, the MegaWizard® Plug-In Manager defaults to the 10-bit /K28.5/ code as the comma character. The Quartus® II software automatically sets the options related to the word aligner, and you cannot change these options in GigE mode. This module matches the 10-bit comma with the data and its complement in the current word boundary. Both positive and negative disparities are checked in this mode. For example, if you specify a /K28.5/ (b’0011111010) pattern as the comma, the rx_patterndetect signal asserts if either the b’0011111010 or b’1100000101 pattern is present in the incoming data.
To use transceiver parameters to set the functional mode, you must preconfigure the receiver with a K28.5 (10’b0101111100 or 10’b1010000011) word align pattern (ALIGN_PATTERN = 0101111100 or ALIGN_PATTERN = 1010000011). Set the ALIGN_PATTERN_LENGTH to 10, even though a 7-bit comma string (7’b0011111 as a comma- or 7’b1100000 as a comma+) is allowed, as stated in the IEEE 802.3 specification. This 7-bit comma is part of the /K28.1/, /K28.5/, and /K28.7/ code-groups. Use a 10-bit /K28.5/ code group to prevent a 7-bit comma from being detected across boundaries when a /K28.7/ code is followed by a /K28.x/, /D3.x/, /D11.x/, /D12.x/, /D19.x/, /D20.x/, or /D28.x/ code group, where x is a value from 0 to 7. Figure 6–5 shows this situation.
Figure 6–5. A Cross-boundary 7-bit Comma When a /K28.7/ Code is Followed by a /K28.5/ Code
K28.7 K28.5
0 0 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1 0 1 0
7-bit comma- 7-bit comma+
The receiver sends a K28.4 (8’h9c + rx_ctrldetect) code from the rx_out[] port and deasserts the rx_syncstatus (1’b0) signal when the receiver is not synchronized. When synchronized, the receiver asserts the rx_syncstatus (1’b1) signal. This signal is aligned with the first valid data received from the rx_out[] port.
Figure 6–6 shows the waveforms related to receiver synchronization. The rx_syncstatus signal goes high when synchronization is complete, indicating that the data is valid. In the example, D1 is the first valid data.
6–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–6. Example of Completed Synchronization
clock
rx_out[7:0] K28.4 K28.4 K28.4 D1 D2 D3 D4 D5
rx_syncstatus
The receiver remains synchronized until it detects a series of bad code groups or is reset. The IEEE 802.3 standard defines the bad code group as four invalid code groups separated by fewer than three valid code groups. If the receiver detects the bad code group or is reset, the rx_syncstatus signal goes low, and a /K28.4/ code appears on the rx_out[] port. GigE mode uses an embedded clocking scheme that retimes all data that can potentially alter the code-group boundary. The boundaries of the code-groups are re-aligned through a synchronization process specified in the IEEE 802.3 standard.
Synchronization State Machines Synchronization occurs when the receiver sees three consecutive ordered sets. An ordered set defined for synchronization is a /K28.5/ comma followed by any odd number of valid data code groups (/Dx.y/). Although you can have a number of sync patterns based on the synchronization rule, three sets of {/K28.5/ /Dx.y/} code groups are the fastest way to achieve synchronization.
GigE mode requires a special synchronization sequence that follows the IEEE 802.3 GMII PCS synchronization specification, as shown in Figure 6–7.
Altera Corporation 6–7 January 2005 Stratix GX Transceiver User Guide GigE Mode Receiver Architecture
Figure 6–7. Synchronization Diagram State Machine
6–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Rate Matcher
The GigE mode operates in multi-crystal environments, which can tolerate a frequency variation of ± 100 ppm between crystals. Stratix GX devices have embedded circuitry to perform clock rate compensation by inserting or removing the /I2/ code group from the interpacket gap (IPG) or idle stream. This process is called “rate matching” or “clock rate compensation.”
The IEEE 802.3 standard, clause 36, specifies two idle order sets (/I1/ and /I2/) for the transmitter. The /I1/ ordered set consists of a negative disparity /K28.5/ (10’h283) followed by a /D5.6/ code group. (A /D5.6/ has the same value, 10’h1A5, for the positive and negative disparity versions and has a balanced 10-bit code.) The /I1/ ordered set should be transmitted only once if the running disparity before the idle is positive.
The /I2/ ordered set consists of a positive disparity /K28.5/ (10’h17C) followed by a negative disparity /D16.2/ (10’h289) code group. The /I2/ ordered set can start the idle sequence if the disparity before the idle sequence is negative. Otherwise, /I2/ follows an /I1/ ordered set and is continually transmitted, maintaining a negative running disparity until the end of the IPG.
Figure 6–8 shows a case in which the idle stream starts with an /I1/ followed by /I2/ ordered sets. The running disparity before the idle state is positive, as indicated by the positive disparity /D30.1/.
Figure 6–8. Idle Generation With /I1/ Ordered Set
clock
tx_out 261h 283h 1A5h 17Ch 289h 17Ch 289h 17Ch 289h
Code Group D30.1+ K28.5- D5.6 K28.5+ D16.2- K28.5+ D16.2- K28.5+ D16.2-
GMII Idle /I1/ /I2/ /I2/ /I2/
Figure 6–9 shows cases in which only /I2/ ordered sets are generated. The running disparity is negative before the start of the idle generation, as indicated by the negative disparity /D30.1/. The /D30.1/ code group in Figure 6–8 and Figure 6–9 is intended only for illustrating disparity and is not intended to signify an end of frame (EOF), nor is it required prior to idle generation.
Altera Corporation 6–9 January 2005 Stratix GX Transceiver User Guide GigE Mode Receiver Architecture
Figure 6–9. Idle Generation Without /I1/ Ordered Set
clock
tx_out 25Eh 17Ch 289h 17Ch 289h 17Ch 289h 17Ch 289h
Code Group D30.1- K28.5+ D16.2- K28.5+ D16.2- K28.5+ D16.2- K28.5+ D16.2-
GMII Idle /I2/ /I2/ /I2/ /I2/
Stratix GX devices have a built-in rate matcher that is 12 words deep, which is a FIFO buffer with control logic. Stratix GX devices implement rate matching in GigE mode by adding or removing /I2/ ordered sets. The /I1/ ordered set is not added or removed.
If the rate matching FIFO buffer encounters an almost full condition, an /I2/ ordered set is deleted, as shown in Figure 6–10. If the rate matching FIFO buffer encounters an almost empty condition, an /I2/ ordered set will be added, as shown in Figure 6–11. The position of the /I2/ ordered set that is added to or deleted from the idle stream varies, depending on when the rate matcher encounters the almost full or almost empty condition.
Figure 6–10. Detection of an /I2/ Ordered Set During an Almost Full Condition
/D/ /D//D//D/ /D//S/ /I2/ /I2/ /I1/ to Rate Matcher
from Rate Matcher /D//D//D/ /D//D/ /D/ /S/ /I2/ /I1/
one /I2/ code removed
6–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–11. Addition of an /I2/ Ordered Set During an Almost Empty Condition
/D/ /D//D//D/ /D//S/ /I2/ /I2/ /I1/ to Rate Matcher
from Rate Matcher /D//D//D/ /D//D/ /D/ /S/ /I2/ /I2/ /I2/ /I1/
one /I2/ code added
8B/10B Decoder
The 8B/10B decoder is part of the Stratix GX transceiver block. The purpose of the 8B/10B Decoder is to restore the 8-bit data plus 1-bit control identifier from the 10-bit code.
10-Bit Decoding The 8B/10B decoder translates the 10-bit encoded data into the 8-bit equivalent data or control code. The byte deserializer receives the least significant bit (LSB) of the 10-bit encoded code first, and the most significant bit (MSB) last. The data received must be from the supported Dx.y or Kx.y list. All 8B/10B control signals (disparity error, control detect, and code error) are pipelined with the data in the Stratix GX receiver block and are edge-aligned with the data. Figure 6–12 is a diagram of the 10-bit to 8-bit conversion.
Figure 6–12. 10-Bit to 8-Bit Conversion
jhgf iedcba
9 8 7 6 5 4 3 2 1 0
MSB received LSB received last first
10b-8b conversion
7 6 5 4 3 2 1 0 Parallel Data
HGFEDCBA
Altera Corporation 6–11 January 2005 Stratix GX Transceiver User Guide GigE Mode Receiver Architecture
Reset The rxdigitalreset signal governs the reset condition of the 8B/10B decoder. In reset, the disparity registers are cleared. Upon exiting reset, the 8B/10B decoder starts with either a positive or negative disparity. The decoder calculates the initial running disparity based on the first valid code that is received.
The receiver block must be word-aligned after reset before the 8B/10B decoder can decode valid data or control codes.
Code Error Detect The rx_errdetect signal indicates when the code received contains an error. This port is optional and, if not in use, there is no way to detect whether a code received is valid. The rx_errdetect goes high if a code received is an invalid code, or if it has a disparity error. If a code is received that is not part of the valid Dx.y or Kx.y list, the rx_errdetect signal goes high. This signal is aligned to the invalid code word received at the PLD logic array.
Disparity Error Detector The 8B/10B decoder detects disparity errors based on which 10-bit code it received. The disparity error is indicated at the optional rx_disperr port. The current running disparity is based on the disparity calculation of the last code received. The disparity calculation is described in the 8B/10B code section in the Appendix.
If negative disparity is calculated for the last 10-bit code, a neutral or positive disparity 10-bit code is expected. If the decoder does not receive a neutral or positive disparity 10-bit code, the rx_disperr signal goes high.
If a positive disparity is calculated, a neutral or negative disparity 10-bit code is expected. In this situation, the rx_disperr signal goes high if the code received is not as expected. When the rx_disperr signal is high, the rx_errdetect signal also goes high.
Figure 6–13 shows a case where the disparity is violated. A K28.5 code has an 8-bit value (8’hbc) and a 10-bit value (jhgfiedcba). The 10-bit value is 10’b0011111010 (10’h17c) for RD- or 10’b1100000101 (10’h283) for RD+. If the running disparity at time n – 1 is negative the expected code at time n must be from the RD- column. Because a K28.5 does not have a balanced 10-bit code (having an equal number of 1’s and 0’s), the expected RD code must toggle back and forth between RD- and RD+. At time n + 3, the 8B/10B decoder received an RD+ K28.5 code (10’h283), which would make the current running disparity negative.
6–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
At time n + 4, because the current disparity is negative, a K28.5 from the RD- column is expected, but a K28.5 code from the RD+ is received instead. This disparity prompts the rx_disperr signal to go high during time n + 4 to indicate that this particular K28.5 code contained a disparity error. The current running disparity at the end of time n + 4 is negative because a K28.5 code from the RD+ column was received. Based on the current running disparity at the end of time n + 5, a positive disparity K28.5 code (from the RD-) column is expected at time n + 5.
Figure 6–13. Disparity Error
n n+1 n+2 n+3 n+4 n+5 n+6 n+7
clock
rx_out[7:0 ] BC BC BC BCxx BC BC BC
rx_disperr
rx_errdetect
rx_ctrldetect
Expected RD code RD- RD+RD- RD+ RD- RD- RD+ RD-
RD code received RD- RD+RD- RD+ RD+ RD- RD+ RD-
rx_in 17C 283 17C 283 28317C 283 17C
Control Detect The 8B/10B decoder differentiates between data and control codes using the rx_ctrldetect port. Although this port is optional, there is no way of differentiating a Dx.y code group from a Kx.y code group if the port is unused.
Figure 6–14 shows an example waveform demonstrating the receipt of a K28.5 code (BC + ctrl). The rx_ctrldetect=1’b1 port is aligned with 8’hbc, indicating that it is a control code. The rest of the code received is data.
Altera Corporation 6–13 January 2005 Stratix GX Transceiver User Guide GigE Mode Transmitter Architecture
Figure 6–14. Control Code Detection
clock
rx_out[7:0] 83 78 BC 07 0F 00 BF 3C
rx_ctrldetect
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
Receiver Phase Compensation FIFO Buffer
The receiver phase compensation FIFO buffer is located at the FPGA logic array interface in the receiver block and is four words deep. This FIFO buffer compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
In GigE mode, the write port is clocked by the refclk from the transmitter phase-locked loop (PLL). The read clock is clocked by CORECLK (output from the transmitter PLL). The receiver phase compensation FIFO buffer can only account for phase differences and must be derived from the recovered clock of its associated channel.
The receiver phase compensation FIFO buffer is always used, and you cannot bypass it.
GigE Mode Figure 6–15 shows the digital components of the Stratix GX transmitter Transmitter that are active in GigE mode. Architecture
6–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–15. Block Diagram of Transmitter Components Configured in GigE Mode
Analog Section Digital Section
Reference Transmitter Clock PLL
Phase 8B/10B Byte Compensation Serializer Encoder Serializer FIFO Buffer
Transmitter
The transmitter architecture includes:
■ Transmitter phase compensation FIFO buffer ■ GigE transmitter synchronization ■ Idle generation ■ 8B/10B encoder
Transmitter Phase Compensation FIFO Buffer
The transmitter phase compensation FIFO buffer is located at the FPGA logic array interface in the transmitter block and is four words deep. The phase compensation FIFO buffer compensates for the phase difference between the clock in the FPGA and the operating clocks in the transceiver block.
The transmitter PLL output clock (refclk) clocks the read port of the phase compensation FIFO buffer. The TX_CORECLK port clocks the write clock. You can select the TX_CORECLK port as an optional transmitter input port to use as a write-side clock of the FIFO buffer. Make sure that there is no frequency difference between the TX_CORECLK port and the transmitter PLL clock. The transmitter phase compensation FIFO only accounts for phase differences.
If you do not select the TX_CORECLK port as an optional input transmitter port, the CORECLK_OUT port feeds the TX_CORECLK port. This connection occurs using the logic array routing. As a result, the software defaults to using an FPGA global clock, regional clock, or fast regional clock resource.
Altera Corporation 6–15 January 2005 Stratix GX Transceiver User Guide GigE Mode Transmitter Architecture
The transmitter phase compensation FIFO buffer is always used, and you cannot bypass it. The input to the transmitter phase compensation FIFO buffer is the data from the PLD logic array. The tx_ctrlenable and tx_forcedisparity signals are also passed through the FIFO buffer to ensure that they are synchronized with the data when they feed to the subsequent module.
GigE Transmitter Synchronization
The transmitter must send out the GigE synchronization sequence to synchronize the target receiver. Stratix GX devices do not have a built-in macro that performs this function on power-up or txdigitalreset. This function must be implemented in user logic to send out a /K28.5/, /Dx.y/, /K28.5/, /Dx.y/, /K28.5/, /Dx.y/ sequence.
Figure 6–16 shows an example of the GigE synchronization pattern. Although the example shows one D0.0 (8’h00) as the /Dx.y/ code, any /Dx.y/ and any odd number of /Dx.y/ can be used.
Figure 6–16. Example of a GigE Synchronization Transmit Pattern
GigE Synchronization Pattern
clock
rx_out[7:0] 00 BC 00 BC 00 BC 00 8D A4
tx_ctrlenable
Idle Generation
In GigE mode, the transmitter replaces any /Dx.y/ code group following a /K28.5/ comma with either a /D5.6/ (8’hc5) or a /D16.2/ (8’h50), depending on the current running disparity, except when the data following the /K28.5/ is /D21.5/ (8’hb5) or /D2.2/ (8’h42). This replacement is to ensure the generation of /I1/ (/K28.5/, /D5.6/) and /I2/ (/K28.5/, /D16.2/) ordered sets and to let the configuration ordered sets /C1/ (/K28.5/, /D21.5/) and /C2/ (/K28.5/, /D2.2/) be received. If the running disparity before the idle ordered set is positive, an /I1/ is chosen. If the running disparity is negative, an /I2/ is chosen. The disparity at the end of an /I1/ is the opposite of the disparity at the beginning of the /I1/. However, the disparity at the end of an /I2/ is
6–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
the same as the beginning running disparity (right before the idle code). This rule ensures a negative running disparity at the end of an idle ordered set. A /Kx.y/ following a /K28.5/ is not replaced.
Figure 6–17 shows the input data codes versus the output data codes. The /D14.3/, /D24.0/, and /D15.8/ code groups were replaced by /D5.6/ or /D16.2/ (for /I1/ and /I2/ ordered sets), and /D21.5/ (part of the /C2/ ordered set) was not replaced.
Figure 6–17. Input Data Codes vs. Output Data Codes
clock
tx_in[ ] K28.5 D14.3 K28.5 D24.0 K28.5 D15.8 K28.5 D21.5 Dx.y
tx_out Dx.y K28.5 D5.6 K28.5 D16.2 K28.5 D16.2 K28.5 D21.5
Order Set /I1/ /I2/ /I2/ /C2/
8B/10B Encoder
The 8B/10B encoder is part of the Stratix GX transceiver block. The 8B/10B encoder translates 8-bit data and a 1-bit control identifier (by using the tx_ctrlenable signal) into a 10-bit, DC-balanced data stream.
For more information about the 8B/10B code, refer to the 8B/10B Code section in the Appendix. The 8B/10B encoder translates the 8-bit data or 8-bit control character to its 10-bit equivalent. Figure 6–18 shows the conversion format. The serializer sends the 10-bit data in order from LSB to MSB.
Altera Corporation 6–17 January 2005 Stratix GX Transceiver User Guide GigE Mode Transmitter Architecture
Figure 6–18. 8B/10B Conversion Format
7 6 5 4 3 2 1 0
HGFEDCBA
8b-10b conversion
jhgf iedcba
9 8 7 6 5 4 3 2 1 0
MSB sent LSB sent last first
Reset After power up or reset, the 8B/10B encoder in GigE mode sends three /K28.5/ commas before user data can be sent. These commas affect the synchronization-ordered set transmission.
After reset (txdigitalreset), three /K28.5/ commas are sent automatically by the 8B/10B encoder. Depending on when you start outputting the synchronization sequence, there are an even or odd number of /Dx.y/ code groups sent by the transmitter before the synchronization sequence. The last of three automatically sent /K28.5/ commas and the first user-sent /Dx.y/ code groups are considered as one idle ordered set. This fact can be a problem if there are even numbers of /Dx.y/ code groups transmitted before the start of the synchronization sequence.
Figure 6–19 shows an example of an even number of /Dx.y/ code groups between the last automatically sent /K28.5/ comma and the first user sent /K28.5/. The first user-sent ordered set is ignored, so three additional ordered sets are required for proper synchronization. Although one set of invalid data is shown between the txdigitalreset signal going low and the first of three automatic K28.5, there can be more than one invalid data set.
6–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–19. Even Number of /Dx.y/ Between Last Automatically Sent /K28.5/ & the First User-Sent /K28.5/
clock
txdigitalreset
tx_out[9:0 ] K28.5 xxx K28.5 K28.5 K28.5 Dx.y Dx.y K28.5 Dx.y K28.5 Dx.y K28.5 D.xy K28.5 Dx.y
First Ordered Set Three Ordered Sets for Syncrhonization Invalid Ordered Set Even Number of /Dx.y/
Control Code Encoding The tx_ctrlenable[] signal determines when a control code must be inserted in the encoded data flow. When the tx_ctrlenable[] signal is low, the byte at tx_in[] is encoded as data. When the tx_ctrlenable[] signal is high, tx_in[] is encoded as a control word. The waveform in Figure 6–20 shows that the second 0xBC is encoded as a control code. The rest are encoded as data.
Figure 6–20. Control Word Identification Waveform
clock
tx_in[7:0] 83 78 BC BC 0F 00 BF 3C
tx_ctrlenable
Code Group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
The 8B/10B encoder does not check that the code word you entered is one of the 12 valid codes. If an invalid control code is entered, the resulting 10-bit code is encoded as either invalid code (that does not map to a valid /Dx.y/ or /Kx.y/ code), or valid /Dx.y/ code, depending on the value entered.
An example is the invalid encoding of a /K24.1/ (data = 8’h38 + tx_ctrlenable = 1’b1). Depending on the current running disparity, the /K24.1/ can be encoded to be 10’b0110001100 (0x18C), which is equivalent to a /D24.6/+ (0xD8 from the RD+ column). An 8B/10B decoder decodes this incorrectly (based on the 8B/10B Fibre Channel specification).
Altera Corporation 6–19 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
GigE Mode GigE Mode Channel Clocking Clocking This section describes the details of clocking the transceiver, the internal clocking details, and the external clock ports in GigE mode. Each block diagram shows the input and output port clocks. The MegaWizard Plug-In Manager by default selects a set of clocks for transmitters and receivers in a transceiver when GigE mode is selected. The wizard also offers clock options, other than default, to facilitate your clocking schemes.
Figure 6–21. Default Configuration of altgxb Megafunction in GigE Mode
6–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–21 shows the altgxb megafunction configured so that the training receiver PLL with the transmitter PLL is enabled. The transmitter PLL is fed from an inclk port that can, in turn, be fed from a dedicated REFCLKB, global clock, regional clock, or fast regional clock source. The receiver logic is clocked by the recovered clock from the clock recovery unit up to the deskew FIFO buffer in the data path. Rate matching occurs between the recovered clock of the channel and refclk from the transmitter PLL. The data from the receiver’s parallel interface is clocked by coreclk_out from the transmitter PLL. On the transmitter channel, the output of the transmitter PLL, coreclk_out, is sent from the logic array as an output and also loops back to clock the write side of the transmit phase compensation FIFO buffer (in this case, software automatically routes the connection) and the read side of the receive phase compensation FIFO buffer.
The training receiver PLL clock recovery unit (CRU) clock from the transmitter PLL can be disabled in the altgxb MegaWizard tool. Deselecting this option adds an additional RX_CRUCLK input reference clock port for the receiver PLL. This feature supports additional multiplication factors for the receiver PLL and also enables the separation of receiver and transmitter reference clocks. This configuration is shown in Figure 6–22.
f For more information on parallel interface speeds, refer to the Stratix GX FPGA Family data sheet.
Altera Corporation 6–21 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
Figure 6–22. Receiver PLL CRU Clock From Transmitter PLL is Disabled by Adding RX_CRUCLK
If the TX_CORECLK is enabled, the training receiver CRU clock from transmitter PLL is not enabled, and other default options are also enabled, this configuration has an independent rx_cruclk port that feeds the receiver PLL reference clock. This input clock port is available only when the receiver PLL is not trained by the transmitter PLL.
6–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
You can optionally enable the write clock of the transmitter phase compensation FIFO buffer to feed in a clock from the PLD logic array.
For example, if all the transmitter channels between transceiver blocks are from a common clock domain, the transceiver instantiations can use a total of one global resource versus one global per transceiver block if the TX_CORECLK option is not enabled. On the transmitter functionality screen and the “optional port of transmitter” section, if TX_CORECLK is selected as an input port, the default clocking scheme changes by using TX_CORECLK as the write clock for the phase compensation FIFO buffer. The user needs to connect CORECLK_OUT to TX_CORECLK using either gclk/rclk/fclk or logic array routing if CORECLK_OUT must be used. Alternatively, TX_CORECLK is supplied from a crystal or any other clock source, as long as it is frequency-locked to the read side of the phase compensation FIFO buffer on the transmit side.
In multicrystal environments, individual recovered clocks need to drive the read clock of the phase compensation FIFO. The Quartus® II software does this by default; you are not required to manually make the connection. tx_coreclk must be frequency matched with its respective read ports. The phase compensation FIFO buffer can only correct for phase, not for frequency differences. The receive parallel interface clocks the data to PLD based on CORECLK_OUT (the default option in the MegaWizard Plug-In Manager). RX_CORECLK is used as the read clock for the rate matching FIFO buffer. Before you can enable this feature, you must set the receiver to 8-bit mode.
Figure 6–23 shows the clock configuration with these optional input ports enabled.
Altera Corporation 6–23 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
Figure 6–23. TX_CORECLK & RX_CORECLK Enabled With RX_CRUCLK Port Note (1)
Note to Figure 6–23: (1) The RX_CORECLK port is enabled for the rate-matching FIFO buffer.
Table 6–2 summarizes the clocks that are used in GigE mode.
Table 6–2. Clocks in GigE Mode (Part 1 of 2)
Clock Port Description INCLK Input Input to transmitter PLL. Available as a port when transmitter PLL is instantiated. RX_CRUCLK Input Input to CRU. Available as a port when CRU is not trained by transmitter PLL.
6–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Table 6–2. Clocks in GigE Mode (Part 2 of 2)
Clock Port Description TX_CORECLK Input Clocks the write port of transmitter phase compensation FIFO buffer. Optional port in Quartus II software. Must be frequency matched to TX_PLL_CLK. If not available as a port, is fed by CORECLK_OUT through logic array routing. RX_CORECLK Input Clocks the read port of receiver phase compensation FIFO buffer. Optional port in Quartus II software. If not available as a port, is fed by CORECLK_OUT through logic array routing. CORECLK_OUT Output Output clock from transmitter PLL equivalent to TX_PLL_CLK. Available as a port if transmitter PLL is used.
GigE Mode Inter-Transceiver Clocking
This section provides guidelines for using transceiver interface clocking between the PLD logic array and transceiver channels when multiple transceiver blocks are active. Depending on which mode is supported by Stratix GX devices, each transceiver block has different transceiver-to- PLD interface clocking. Different input and output clocks are available based on the options provided by Quartus II MegaWizard built-in functions. The number of supported channels varies based on the type of Stratix GX device you select. Because of the various configurations of the input and output clocks, consider the clocking schemes between transceiver blocks carefully to avoid future problems in the design cycle.
One of the clocking interfaces to consider while designing with Stratix GX is the transceiver-to-PLD interface. This clocking scheme can be further classified as the PLD-to-transmitter channel and receiver channel to the PLD.
In GigE mode, the read port of the transmitter phase compensation FIFO buffer can either be clocked by the CORECLK_OUT or the TX_CORECLK port. The constraint on using TX_CORECLK port is that the clock must be frequency locked to the read port of the transmitter phase compensation FIFO buffer. Synchronous data transfers for a multi-transceiver configuration are accomplished with the TX_CORECLK port. The TX_CORECLK of multiple transceivers can be connected to a common clock domain, either from a single CORECLK_OUT signal or from a PLD system clock domain. This scheme is shown in Figure 6–24.
Altera Corporation 6–25 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
Figure 6–24. Example of a Multi-Transceiver PLD to Transmitter Interface Clocking Scheme
ALTGXB PLD
coreclk_out[0]
Transceiver Block 0 tx_in_0[15..0]
tx_coreclk[0]
coreclk_out[1] tx_in_1[15..0] Transceiver Block 1 tx_coreclk[1] tx_coreclk[1]
PLD Transmit Data Clock Domain coreclk_out[2]
Transceiver Block 2 tx_in_2[15..0]
tx_coreclk[2]
coreclk_out[3] tx_in_3[15..0] Transceiver Block 3 tx_coreclk[3]
When TX_CORECLK is not enabled, the Quartus II software automatically routes the signal from the CORECLK_OUT port to the write clock of the phase compensation FIFO buffer using a global, regional, or fast regional resource. In a multi-transceiver configuration, this routing can lead to timing violations because the coreclk_out per transceiver block cannot guarantee a phase relationship. Therefore, clocking the TX_CORECLK with a common clock is recommended for synchronous transmission.
Another inter-transceiver consideration is the selection of the dedicated REFCLKB pin. Stratix GX channels are arranged in banks of four (called transceiver blocks). Each transceiver block has the ability to share a common reference clock through the inter-transceiver lines (IQ lines). The Stratix GX logic array clock usage can be reduced by using the IQ lines. The IQ lines are used when a REFCLKB input port from one transceiver block or channel drives other transceiver blocks or channels. The Quartus I software automatically determines the IQ line usage.
6–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
When determining the location of REFCLKB pins, consider what can be fed by the pin you choose. Table 6–3 shows the available IQ lines and which transceiver block REFCLKB drives the REFCLKB pin. This data is based on the number of transceiver channels in the Stratix GX device.
Table 6–3. REFCLKB Pin to Inter-Transceiver Line Connections
REFCLKB Pin in Inter-Transceiver Channels in Channel Density Transceiver Block Line Driven by Transceiver Block Number REFCLKB 8 channels 0 [3:0] IQ2 (EP1SGX10) 1 [7:4] IQ0 16 channels 0 [3:0] — (EP1SGX25) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 20 channels 0 [3:0] — (EP1SGX40) 1 [7:4] IQ2 2 [11:8] IQ0 3 [15:12] IQ1 4 [19:16] —
Figure 6–25 shows the transceiver routing with respect to inter- transceiver lines for the EP1SGX25F device. Be sure to use this information when placing REFCLKB pins. (When placing refclkb pins, see Appendix C, REFCLKB Pin Constraints for information about analog reads and refclkb pin usage constraints.) For example, if a REFCLKB pin is required to feed a transmitter PLL using an inter-transceiver line, the REFCLKB pin cannot be in transceiver block 1, because IQ2 only feeds the receiver PLLs.
Altera Corporation 6–27 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
Figure 6–25. Inter-transceiver Line Connections for EP1SGX25F Device
Transceiver Block 0
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 IQ0 IQ1 IQ2 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 1
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 2 16
PLD Global Clocks IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
Transceiver Block 3
IQ0 IQ1 Transmitter Global Clocks, I/O Bus, General Routing PLL
refclkb /2
IQ2 4 4 Global Clocks, I/O Bus, General Routing Receiver PLLs
6–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–26 shows the transceiver routing with respect to inter- transceiver lines for the EP1SGX40G device. This device has an extra transceiver block (number 4), which is in the middle of all the transceiver blocks, as illustrated. Be sure to use this information when placing REFCLKB pins. (When placing refclkb pins, see Appendix C, REFCLKB Pin Constraints for information about analog reads and refclkb pin usage constraints.) For example, if a REFCLKB pin is required to feed a transmitter PLL using an inter-transceiver line, the REFCLKB pin cannot be in transceiver block 1, because IQ2 only feeds the receiver PLLs.
Altera Corporation 6–29 January 2005 Stratix GX Transceiver User Guide GigE Mode Clocking
Figure 6–26. Inter-transceiver Line Connections for EP1SGX40G Device
Transceiver Block 0
IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 1 IQ0 IQ1 IQ0 IQ1 IQ2 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 4 PLD
IQ0 Global IQ1 Global Clks, I/O Bus, Gen Routing TX PLL Clocks refclkb 16 /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
Transceiver Block 2 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 Global Clks, I/O Bus, Gen Routing 4 4 Receiver PLLs
Transceiver Block 3 IQ0 IQ1 Global Clks, I/O Bus, Gen Routing TX PLL refclkb /2 IQ2 4 Global Clks, I/O Bus, Gen Routing 4 Receiver PLLs
6–30 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
GigE Mode This section describes the altgxb megafunction options for GigE mode. Altera® recommends that the Stratix GX transceiver block be instantiated MegaWizard and parameterized through the altgxb MegaWizard Plug-In Manager in the Quartus II software. The Quartus II MegaWizard Plug-In Manager altgxb-In offers a graphical user interface (GUI) that organizes the altgxb options in easy-to-use sections. The MegaWizard Plug-In Manager also sets the correct ports and parameters automatically, based on the options and parameters you select. Invalid settings are automatically flagged in the wizard to avoid illegal configurations. The MegaWizard Plug-In also disables any options that do not apply to GigE mode.
Although you can instantiate the Stratix GX block directly by calling out the altgxb megafunction, Altera recommends that you use the MegaWizard Plug-In Manager to instantiate your altgxb megafunction to reduce the chance of invalid settings.
GigE Mode MegaWizard Considerations
Each altgxb MegaWizard instantiation can use one or more transceiver blocks, based on the number of channels you select. There are four channels per transceiver block. If a MegaWizard instantiation uses fewer than four channels, the remaining channels in that transceiver block are no longer available for use.
Each MegaWizard instantiation must have similar functionality and data rates. If you wish to have transceiver blocks that differ in functionality or data rates, you can create a separate MegaWizard instantiation for each transceiver block.
Also, as mentioned in the clocking section, the MegaWizard displays the configuration of the altgxb megafunction. This diagram changes dynamically based on the selected mode, options, and clocking schemes.
GigE Mode altgxb MegaWizard Options
Figures 6–27 through 6–33 show the MegaWizard Plug-In Manager pages where you select the options for a GigE mode configuration.
Altera Corporation 6–31 January 2005 Stratix GX Transceiver User Guide GigE Mode MegaWizard
Figure 6–27. MegaWizard Plug-In Manager - ALTGXB (Page 3 of 9) - General (1) Notes (1)–(5)
Notes to Figure 6–27: (1) GigE protocol mode supports duplex, receiver-only, or transmitter-only operation modes. (2) Valid numbers: 1 to Max Channels available on the device. The Quartus II software automatically assigns the channels to a transceiver block unless input/output pin assignments are made to the channel’s transceiver input and output pins. (3) 8 bits: single width (4) For more information, refer to the Stratix GX Analog Description chapter. (5) rxdigitalreset: resets the digital blocks in the receiver channel. Each active receiver channel has its own digital reset. txdigitalreset: resets the digital blocks of the transmitter channel. Each active transmitter channel has its own digital reset. rxanalogreset: Resets the receiver’s analog circuits and the receiver PLL. Each active receiver channel contains its own analog reset. pll_areset: Resets the entire transceiver block: all receiver and transmitter digital and analog circuits, including receiver and transmitter PLLs.
6–32 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–28. MegaWizard Plug-In - ALTGXB (Page 4 of 9) - General (2) Notes (1), (2)
Notes to Figure 6–28: (1) For more information, refer to the Loopback Modes chapter. (2) For more information, refer to the Stratix GX Built-In Self Test (BIST) chapter.
Altera Corporation 6–33 January 2005 Stratix GX Transceiver User Guide GigE Mode MegaWizard
Figure 6–29. MegaWizard Plug-In Manager - ALTGXB (Page 5 of 9) - Receiver (1) Notes (1)–(3)
Notes to Figure 6–29: (1) Enable this if the device is an engineering sample device. (2) For more information, refer to the Stratix GX Analog Description chapter. (3) The word aligner in GigE mode is always set as a 10-bit K28.5 pattern. Both positive and negative disparities are checked.
6–34 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–30. MegaWizard Plug-In Manager - ALTGXB (Page 6 of 9) - Receiver (2) Notes (1)–(3)
Notes to Figure 6–30: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) The GigE data rate is set to 1250 Mbps by default. Possible multiplication factors of the input clock are 2, 4, 5, 8, 10, 16, and 20. Multiplication factors of 2, 4, and 5 must use the refclkb pins. A multiplication factor of 2 also requires that the receiver PLL be trained by the transmitter PLL. (3) The force signal detection option is always on; you cannot turn it off. Because the signal detect circuitry is always forced, the rx_signaldetect signal is always set in GigE mode.
Altera Corporation 6–35 January 2005 Stratix GX Transceiver User Guide GigE Mode MegaWizard
Figure 6–31. MegaWizard Plug-In Manager - ALTGXB (Page 7 of 9) - Receiver (3) Notes (1)–(5)
Notes to Figure 6–31: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) Receiver PLL lock indicator. For rx_locked, Low = receiver PLL locked to reference clock. (3) The rx_signaldetect is only available in XAUI or GigE mode. Refer to the Stratix GX Analog Description chapter for additional information. (4) Indicates when the word aligner has aligned to the byte boundary. The rx_syncstatus signal goes high for one rx_clkout period when the word aligner aligns to the new byte boundary. (5) The rx_patterndetect is similar to the rx_syncstatus, with the exception that the rx_patterndetect asserts only when the Word Alignment pattern appears in the data stream within the synchronized byte boundary.
6–36 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–32. MegaWizard Plug-In Manager - ALTGXB (Page 8 of 9) - Transmitter Notes (1), (2)
Notes to Figure 6–32: (1) For more information, refer to the Stratix GX Analog Description chapter. (2) tx_coreclk. You can optionally choose the write clock of the transmitter phase comp FIFO buffer. This clock should be frequency locked with the internal reference clock because the phase comp FIFO buffer cannot tolerate frequency variations and contains no error flags.
Altera Corporation 6–37 January 2005 Stratix GX Transceiver User Guide Design Example
Figure 6–33. MegaWizard Plug-In Manager - ALTGXB (Page 9 of 9) - Summary
Design Example The design example shows the GigE synchronization sequence and illustrates what happens when the receiver loses synchronization, as described in clause 36 of the IEEE 802.3 specification. To simplify the documentation process, the design is implemented in Verilog hardware description language (HDL).
Design Description
When the protocol is specified as GigE, synchronization is achieved on receiving three (/K28.5/, /Dx.y/) ordered sets. Each /K28.5/ is separated by any odd number of /Dx.y/ code groups. Invalid code groups are not supported during the synchronization stage. If at any time four invalid code groups are received separated by fewer than three valid code groups, synchronization is lost. This design example shows both the transmission of the synchronization sequence and the transmission of the invalid error codes that cause the loss of synchronization.
`define reset 3'd0 `define donothing 3'd1 `define sync 3'd2 `define tx_err 3'd3
6–38 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
`define count 3'd4 `define txk 3'd5 module gige8b10btest( clk, rx_in, patterndetect, ctrldetect, errdetect, syncstatus, disperr, rxout, txout); input clk, rx_in; output patterndetect, ctrldetect, errdetect,syncstatus,disperr; output [7:0] rxout; output txout; reg [3:0] curst,nextst; reg reset, txctrl; reg [6:0] globalcntr; reg [3:0] kcntr; reg [7:0] datacntr, kdata,txdata; reg tff; wire [7:0] rxout; wire coreclk, rxclk, rx_in; wire patterndetect, ctrldetect, errdetect,syncstatus,disperr; //GXB instantiation gige8b10bgxb gige8b10bgxb_inst( .pll_areset(1'b0), .pllenable(1'b1), .inclk(clk), .rx_in(rx_in), .rx_slpbk(1'b1), .rxanalogreset(1'b0), .tx_in(txdata), .tx_ctrlenable(txctrl), .rxdigitalreset(reset), .txdigitalreset(1'b0), .rx_disperr(disperr), .rx_patterndetect(patterndetect), .rx_ctrldetect(ctrldetect), .tx_out(txout), .rx_errdetect(errdetect), .coreclk_out(coreclk), .rx_out(rxout), .rx_syncstatus(syncstatus)); //governing counter always@(posedge clk) globalcntr <= globalcntr +1; //control character counter always@(posedge clk)
Altera Corporation 6–39 January 2005 Stratix GX Transceiver User Guide Design Example
if(kcntr==4'd11 || reset==1'b1) kcntr<=4'b0; else kcntr<=kcntr+1; //data counter always@(posedge clk or posedge reset) if(reset==1'b1) datacntr<=1'b0; else datacntr<=datacntr+1; //control character decode always@(kcntr) case (kcntr) 0: kdata=8'h1c; //k28.0 1: kdata=8'h3c; //k28.1 2: kdata=8'h5c; //k28.2 3: kdata=8'h7c; //k28.3 4: kdata=8'h9c; //k28.4 5: kdata=8'hbc; //k28.5 6: kdata=8'hdc; //k28.6 7: kdata=8'hfc; //k28.7 8: kdata=8'hf7; //k23.7 9: kdata=8'hfb; //k27.7 10: kdata=8'hfd; //k29.7 11: kdata=8'hfe; //k30.7 // 12: kdata=8'hff; //invalid code default:kdata=8'hbc; endcase always@(globalcntr or curst) case(globalcntr) 0: nextst=`reset;//resets receiver 1: nextst=`sync; //sends out 3 idle ordered sets 8: nextst=`count; //sending counter values 40: nextst=`txk; //sending control characters 52: nextst=`count; //sending counter values 60: nextst=`tx_err; //sending 4 illegal codes 64: nextst=`donothing; //do nothing until resync default: nextst= curst; endcase always @(posedge clk) curst<=nextst; always@(posedge clk) case(curst) `reset: //resets receiver
6–40 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
begin reset<=1; txctrl<=0; txdata<=datacntr; end `donothing: //sends out /D0.0/ begin reset<=0; txctrl<=0; txdata<=8'h00; end `sync: //sends alternating /K28.5/ and /D31.7/ begin reset<=0; if (globalcntr[0]==1) begin txdata<=8'hbc; txctrl<=1; end else begin txdata<=8'hff; txctrl<=0; end end `tx_err: //sends an out of bounds control code /K31.7/ begin reset<=0; txctrl<=1; txdata<=8'hff; end `count: //sends out value of a counter begin reset<=0; txctrl<=0; txdata<=datacntr; end `txk: //sends out all 12 K codes begin reset<=0; txctrl<=1; txdata<=kdata; end default: begin reset<=0; txctrl<=0; txdata<=datacntr; end endcase endmodule
Altera Corporation 6–41 January 2005 Stratix GX Transceiver User Guide Design Example
ALTGXB
module gige8b10bgxb ( pll_areset, pllenable, inclk, rx_in, rx_slpbk, rxanalogreset, tx_in, tx_ctrlenable, rxdigitalreset, tx_forcedisparity, txdigitalreset, rx_disperr, rx_patterndetect, rx_ctrldetect, tx_out, rx_errdetect, coreclk_out, rx_out, rx_syncstatus); input[0:0] pll_areset; input[0:0] pllenable; input[0:0] inclk; input[0:0] rx_in; input[0:0] rx_slpbk; input[0:0] rxanalogreset; input[7:0] tx_in; input[0:0] tx_ctrlenable; input[0:0] rxdigitalreset; input[0:0] tx_forcedisparity; input[0:0] txdigitalreset; output[0:0] rx_disperr; output[0:0] rx_patterndetect; output[0:0] rx_ctrldetect; output[0:0] tx_out; output[0:0] rx_errdetect; output[0:0] coreclk_out; output[7:0] rx_out; output[0:0] rx_syncstatus; wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] sub_wire2; wire [0:0] sub_wire3; wire [7:0] sub_wire4; wire [0:0] sub_wire5; wire [0:0] sub_wire6; wire [0:0] sub_wire7; wire [0:0] rx_disperr = sub_wire0[0:0]; wire [0:0] rx_patterndetect = sub_wire1[0:0];
6–42 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
wire [0:0] tx_out = sub_wire2[0:0]; wire [0:0] rx_ctrldetect = sub_wire3[0:0]; wire [7:0] rx_out = sub_wire4[7:0]; wire [0:0] rx_errdetect = sub_wire5[0:0]; wire [0:0] coreclk_out = sub_wire6[0:0]; wire [0:0] rx_syncstatus = sub_wire7[0:0]; altgxbaltgxb_component ( .pll_areset (pll_areset), .pllenable (pllenable), .inclk (inclk), .rx_in (rx_in), .rx_slpbk (rx_slpbk), .tx_in (tx_in), .rxanalogreset (rxanalogreset), .tx_ctrlenable (tx_ctrlenable), .rxdigitalreset (rxdigitalreset), .tx_forcedisparity (tx_forcedisparity), .txdigitalreset (txdigitalreset), .rx_disperr (sub_wire0), .rx_patterndetect (sub_wire1), .tx_out (sub_wire2), .rx_ctrldetect (sub_wire3), .rx_out (sub_wire4), .rx_errdetect (sub_wire5), .coreclk_out (sub_wire6), .rx_syncstatus (sub_wire7)); defparam altgxb_component.force_disparity_mode = "ON", altgxb_component.channel_width = 8, altgxb_component.pll_inclock_period = 7812, altgxb_component.use_symbol_align = "ON", altgxb_component.rx_ppm_setting = 1000, altgxb_component.pll_bandwidth_type = "LOW", altgxb_component.dwidth_factor = 1, altgxb_component.number_of_channels = 1, altgxb_component.vod_ctrl_setting = 1000, altgxb_component.align_pattern_length = 10, altgxb_component.use_self_test_mode = "OFF", altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON", altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.equalizer_ctrl_setting = 0, altgxb_component.use_auto_bit_slip = "ON", altgxb_component.use_rate_match_fifo = "ON", altgxb_component.signal_threshold_select = 80, altgxb_component.use_double_data_mode = "OFF", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "GIGE", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.rx_bandwidth_type = "LOW", altgxb_component.disparity_mode = "ON",
Altera Corporation 6–43 January 2005 Stratix GX Transceiver User Guide Design Example
altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.loopback_mode = "SLB", altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.use_equalizer_ctrl_signal = "OFF", altgxb_component.rx_enable_dc_coupling = "OFF", altgxb_component.run_length_enable = "OFF", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "DUPLEX", altgxb_component.use_8b_10b_mode = "ON", altgxb_component.use_rx_clkout = "OFF", altgxb_component.data_rate_remainder = 0, altgxb_component.data_rate = 1280, altgxb_component.align_pattern = "P0101111100", altgxb_component.use_rx_cruclk = "OFF", altgxb_component.number_of_quads = 1; endmodule
Simulation Waveform & Hardware Verification Results
Figures 6–34 and 6–35 show the complete synchronization sequence from the transmitter to the receiver for the SignalTap® II logic analyzer and the Quartus II software, respectively. The GigE duplex channel is configured in a serial loopback mode. The synchronization pattern is sent by the transmitter. The receiver sends a K28.4 character (8’ b9C + ctrl) until synchronization is achieved. Although any odd number of valid /Dx.y/ codes is supported between each /K28.5/ code, one /Dx.y/ is shown in this example.
The 8’h00 shown on the rx_out bus results from the reset pulse when the pipelined registers are reset in the receiver block.
There is good correlation between the SignalTap II logic analyzer results and the Quartus II software simulation.
Figure 6–34. GigE Synchronization Sequence SignalTap II Results
6–44 Altera Corporation Stratix GX Transceiver User Guide January 2005 GigE Mode
Figure 6–35. GigE Synchronization Sequence Quartus II Software Simulation Results
Figures 6–36 and 6–37 show the loss of GigE synchronization on receiving invalid code groups from the SignalTap II logic analyzer and the Quartus II software, respectively. On receiving four invalid codes that are separated by fewer than three valid codes, the receiver signals a loss of synchronization by deasserting the rx_syncstatus signal and sending a /K28.4/ code group (8’h9C + ctrl). In the example, four invalid codes are transmitted with zero valid codes in between.
Figure 6–36. Loss of Synchronization SignalTap II Logic Analyzer Results
Figure 6–37. Loss of Synchronization Quartus II Simulation Results
Altera Corporation 6–45 January 2005 Stratix GX Transceiver User Guide Design Example
6–46 Altera Corporation Stratix GX Transceiver User Guide January 2005 7. Loopback Modes
Introduction You can apply several loopback modes to the Stratix® GX block. The main forms of loopback are as follows:
■ Serial loopback ■ Parallel loopback ■ Reverse serial loopback
Loopback refers to feeding the data from the transmitter directly to the receiver. Reverse loopback refers to feeding the data from the receiver directly to the transmitter. Serial loopback and parallel loopback feed data from the transmitter block to the receiver. Reverse serial loopback feeds the data from the receiver to the transmitter.
Serial Loopback Figure 7–1 shows the data path for serial loopback. A data stream is fed to the transmitter from the FPGA logic array and has the option of using all the blocks in the transmitter. The data then traverses from the transmitter in serial form to the receiver. The serial data is the data that is transmitted from the Stratix GX device. Once the data enters the receiver in serial form, it can use any of the receiver blocks and is then fed into the FPGA logic array. The PRBS block generates data when using serial loopback.
Serial loopback is dynamically enabled on a channel-by-channel basis using the rx_slpbk port. When rx_slpbk is high, all blocks that are active when the signal is low are still active. The serial loopback is enabled but output is still seeing data on the tx_out[] port.
Serial loopback is often used to check the analog portion of the transceiver. The data is retimed through different clock domains and an alignment pattern is still necessary for the word aligner.
Altera Corporation 7–1 January 2005 Parallel Loopback
Figure 7–1. Stratix GX Block in Serial Loopback Mode
BIST PRBS Verifier
BIST Deserializer Word Aligner Incremental Channel Verifier Aligner Rate Matcher 8B/10B Phase Decoder Byte Compensation Clock Deserializer FIFO Recovery Unit
Byte Phase Serializer 8B/10B Serializer Compensation Encoder FIFO BIST Generator Active Path BIST PRBS Generator Non-Active Path
Parallel Figure 7–2 shows the data path for parallel loopback. A data stream is fed to the transmitter from the FPGA logic array and has the option of using Loopback blocks in the transmitter block. The data then exits the transmitter into the receiver in parallel form before entering the serializer. The data enters the receiver block after the deserializer and has the option of using any of the subsequent receiver blocks before being output by the receiver into the FPGA logic array. The PRBS block generates data. When using parallel loopback, the tx_out ports are active, and the differential output voltage on the tx_out ports is based on the current setting in the Quartus® II software or on the user setting.
7–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Loopback Modes
Figure 7–2. Stratix GX Block in Parallel Loopback Mode
BIST PRBS Verifier
BIST Deserializer Word Aligner Incremental Channel Verifier Aligner Rate Matcher 8B/10B Phase Decoder Byte Compensation Clock Deserializer FIFO Recovery Unit
Byte Phase Serializer 8B/10B Serializer Compensation Encoder FIFO BIST Generator Active Path BIST PRBS Generator Non-Active Path
Reverse Serial Figure 7–3 shows the data path for reverse serial loopback. Data comes in from the rx_in ports in the receiver. The data is then fed through the Loopback CDR block in serial form directly to the tx_out ports in the transmitter block.
Reverse serial loopback is enabled for all channels through the software or is dynamically enabled on a channel-by-channel basis using the tx_srlpbk port. When using reverse serial loopback, the VOD must be 400mV.
When tx_srlpbk is high, all blocks that are active when the signal is low are still active. The reverse serial loopback is enabled but the logic array is still seeing data.
Reverse serial loopback is often implemented when using a Bit Error Rate Tester (BERT).
Altera Corporation 7–3 January 2005 Stratix GX Transceiver User Guide Reverse Serial Loopback
Figure 7–3. Stratix GX Block in Reverse Serial Loopback Mode
BIST PRBS Verifier
BIST Deserializer Word Aligner Incremental Channel Verifier Aligner Rate Matcher 8B/10B Phase Decoder Byte Compensation Clock FIFO Deserializer Recovery Unit
Byte Phase Serializer 8B/10B Serializer Compensation Encoder FIFO BIST Generator Active Path BIST PRBS Non-Active Path Generator
7–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 8. Stratix GX Built-In Self Test (BIST)
Introduction Each Stratix® GX channel in the gigabit transceiver block contains embedded built-in self test (BIST) circuitry, which is available for quick device verification. The BIST circuitry consists of a data generator that resides in the transmitter channel and a verifier that resides in the receiver channel. Figure 8–1 shows a simplified block diagram of the BIST circuitry.
Figure 8–1. Image of Stratix GX Built-In Self Test
txdigitalreset[] tx_out[] Built-In Self Test rxdigitalreset[] rx_bisterr[]2 (BIST) rx_slpbk[]1 rx_bistdone[]2 inclk[]
Notes to Figure 8–1: (1) rx_slpbk[] is required in PRBS and incremental BIST modes. (2) rx_bisterr[] and rx_bistdone[] are only available in PRBS and incremental BIST modes.
The BIST data generator is configured to generate pseudo-random binary sequence (PRBS), incremental, high-frequency, low-frequency, or mixed- frequency patterns. The BIST verifier supports only the PRBS and Incremental modes. The remaining BIST modes are intended for quick evaluations of the transmitters. The Quartus® II software simulation models do not support the PRBS patterns generated in the BIST circuit. Figure 8–2 shows the BIST modes.
Altera Corporation 8–1 January 2005 Pattern Generator
Figure 8–2. Block Diagram of BIST Modes
BIST MODES
PATTERN GENERATOR PATTERN VERIFIER (Transmitter) (Receiver)
HIGH LOW MIX INCREMENTAL PRBS PRBS INCREMENTAL Frequency Frequency Frequency
PRBS PRBS PRBS PRBS 10^ 8-1 10^ 10-1 10^ 8-1 10^ 10-1
Pattern The BIST data generator supports the following pattern generators:
Generator ■ PRBS mode generator ■ Incremental mode generator ■ High-frequency mode generator ■ Low-frequency mode generator ■ Mix-frequency mode generator
PRBS Mode Generator
Pseudo-Random Bit Sequences (PRBS) are commonly used to verify the integrity and robustness of the data transmission paths. The PRBS generator is used in 8-, 16-, 10-, or 20-bit modes. In 8- or 16-bit data width modes, the PRBS generator generates 28-1 unique patterns. In 10- or 20-bit data modes, the PRBS generator yields 210-1 unique patterns. Table 8–1 lists the modes and their associated polynomials.
Table 8–1. BIST Generator PRBS Modes
Data Width PRBS Mode Polynomials
8-bit 28-1 X8 + X7 + X5 + X3 + 1 10-bit 210-1 X10 + X7 + 1 16-bit 28-1 X8 + X7 + X5 + X3 + 1 20-bit 210-1 X10 + X7 + 1
8–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Built-In Self Test (BIST)
PRBS mode is enabled when the PRBS option is enabled in the Quartus II software. The 8b-10b encoder/decoder is bypassed automatically in this mode.
You can use PRBS generation to test the functionality of both the transmitter and receiver, to test if the BIST verifier is enabled, or to measure the quality of the transmission medium. The advantage of using a PRBS data stream is that the randomness yields an environment that stresses the transmission medium. In the data stream both random jitter and deterministic jitter are observed either by a time interval analyzer (TIA), a bit error rate tester, or an oscilloscope.
Incremental Mode Generator
In the incremental mode, the data generator sweeps through all the valid 8b/10b data and control characters. You can also enable the incremental BIST verifier to perform a quick verification of the 8B/10B encoder/decoder paths. Refer to “Pattern Verifier” on page 8–5 for more information.
Incremental mode is enabled when option 1 is selected under the what self test mode do you want to use? option in the Quartus II software. In this mode, the BIST generator sends out the data pattern in the following sequence: K28.5 (comma), K27.7 (Start of Frame, SOF), Data (00-FF incremental), K28.0, K28.1, K28.2, K28.3, K28.4, K28.6, K28.7, K23.7, K30.7, K29.7 (End of Frame, EOF) and repeat. The 8b/10b encoder must be enabled for proper operation.
Because the 8/b10b encoder is enabled, the data stream is DC balanced. 8b/10b encoding guarantees a run length less than 5 UI, which yields a less stressful pattern than the PRBS data. However, because the PRBS generator bypasses the 8b/10b paths, you can use the incremental BIST to test this path.
High-Frequency Mode Generator
In high-frequency mode, the BIST generator transmits a D21.5 ±(8'b10110101) character into the 8b/10b encoder to generate a 10'b1010101010 high-frequency character. This toggling data is the highest frequency that the data stream can transmit.
This pattern is DC balanced; the number of ones is equal to number of zeros. This fact is important when trying to perform a first-order random jitter measurement. You can measure this jitter using an oscilloscope with a histogram defined at the zero crossing point. This method is crude, but still yields a first-order estimated value, because the majority of the
Altera Corporation 8–3 January 2005 Stratix GX Transceiver User Guide Pattern Generator
deterministic data dependant components are masked out. However, for more accurate measurements, use a TIA or some type of jitter separation software to break down the random and deterministic components.
High-frequency mode is also useful when trying to characterize the high-frequency losses in the time domain. The delta amplitude difference between the high-frequency pattern and the low-frequency pattern can give you a first-order approximation of the high-frequency losses due to the skin effect and dielectric losses. This method is useful only for a first-order approximation; use extractions of RLGC values with 2D and 3D field solvers to determine more accurate loss coefficients.
High-frequency mode is enabled when option 2 is selected in the Quartus II software under what self test mode do you want to use? Enable the 8b/10b encoder to generate the high-frequency pattern. If it is disabled, an 8'b10110101 character is sent instead of the 10'b1010101010 character.
Low-Frequency Mode Generator
In low-frequency mode, the BIST generator transmits a K28.7 -/+ character (8'b11111100) into the 8b/10b encoder to generate a 10'b0011111000 or 10'b1100000111 low-frequency character. The low-frequency data transition toggles at one-tenth the data rate of the high-frequency pattern.
Like the high-frequency pattern, the low-frequency pattern is DC balanced with the number of ones equal to the number of zeros. This fact is important when trying to perform a first order random jitter measurement. You can measure this jitter using an oscilloscope with a histogram defined at the zero crossing point. This method is crude, but still yields a first-order estimated value, because the majority of the deterministic data-dependant components are masked out. However, for more accurate measurements, use a TIA or some type of jitter separation software to break down the random and deterministic components.
Because the data transitions in a slower frequency, the signal is less prone to high-frequency losses. As a result, the signal is able to rise to a higher amplitude than the high-frequency components. Therefore, the delta between the two measurements yields a first order approximation of the high-frequency losses in the time domain. Once again, this approach is useful only for a first-order approximation. Use extractions of RLGC values with 2D and 3D field solvers to determine more accurate loss coefficients.
8–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Built-In Self Test (BIST)
Low-frequency mode is enabled when you select the SELF_ option 3 in the Quartus II software under what self test mode do you want to use? You must enable the 8b/10b encoder to generate the high-frequency pattern. If it is disabled, an 8'b11111100 character is sent instead of the 10'b0011111000 or 10'b1100000111 characters.
Mix-Frequency Mode Generator
In mix-frequency mode, the BIST generator transmits a K28.5 -/+ character (8'b10111100) character into the 8b/10b encoder to generate a 10'b0011111010 or 10'b1100000101 mixed-frequency character. The mixed frequency pattern contains both high-frequency and low-frequency components. This approach is useful for first-order approximation of the frequency response of the transmission medium. If captured with an oscilloscope, these frequency responses are approximated in time domain.
Mix-frequency mode is enabled when you select option 4 in the Quartus II software under what self test mode do you want to use? As in the high-frequency and low-frequency modes, you must enable the 8b/10b encoder in order to generate the mixed-frequency pattern.
Pattern Verifier The BIST verifier supports the PRBS and incremental modes.
PRBS Mode Verifier
The PRBS verifier provides a quick check through the non-8b/10b path of the transceiver block. You must select the internal or external loopback mode to loop the generated data back into the verifier in the receiver. Select either a serial or parallel loopback to provide this path. A parallel loopback tests the digital portion of the transceiver while a serial loopback also tests the analog clock recovery unit (CRU) and the serializer and deserializer.
The PRBS verifier is active when the receiver channel is synchronized. The alignment pattern must be set to 16'b1000000011111111 for the 8- and 16-bit modes and to 10'b111111111 for the 10- and 20-bit modes. The data is synchronized automatically with a built in state machine, so the rx_enacdet signal is not required.
The verifier stops checking the patterns after receiving all the PRBS patterns (255 patterns for 8-bit mode and 1023 patterns for 10-bit mode). The rx_bistdone signal goes high, indicating that the verifier has completed. If the verifier detects an error before it is finished, rx_bisterr goes high and the value will be latched until it is reset. The rxdigitalreset signal must be used to re-start the PRBS verification.
Altera Corporation 8–5 January 2005 Stratix GX Transceiver User Guide Pattern Verifier
Be sure you do not use the rx_apllreset signal because the re-training process of the CRU might cause false errors. A reference design is included in “Design Examples” on page 8–7.
Incremental Mode Verifier
In the incremental mode, the BIST generator transmits the data pattern in the following sequence: K28.5 (comma), K27.7 (SOF), Data (00-FF incremental), K28.0, K28.1, K28.2, K28.3, K28.4, K28.6, K28.7, K23.7, K30.7, K29.7 (EOF), and repeat.
The sync pattern on the receiver word aligner must be set to a K28.5 pattern (10'b0011111010) for proper synchronization between the generator and verifier. As in the PRBS verification mode, the synchronization is handled by a built-in state machine, so control of the rx_enacdet signal is not required.
The BIST verifier waits for the word aligner to synchronize. After synchronization, the BIST verifier checks for the following sequence: K27.7 (SOF), Data (00-FF incremental), K28.0, K28.1, K28.2, K28.3, K28.4, K28.6, K28.7, K23.7, K30.7, and K29.7 (EOF). If it does not see a K27.7 (SOF) within 31 patterns, the rx_errdetect and rx_bistdone signals go high, and the verifier stops. The verifier checks for this sequence twice before setting the rx_bistdone signal high. If any errors are detected before the verifier finishes, the rx_errdetect and rx_bistdone signals go high. Use the rxdigitalreset signal to restart the incremental verification. Do not use the rx_apllreset signal because the retraining process of the CRU might cause false errors. A reference design is included in “Design Examples” on page 8–7.
Table 8–2 shows which loopback modes are supported for each verification mode.
Table 8–2. Verification Modes
Verification Mode Comma Loopback Modes
28-1 16'b1000000011111111 Serial or parallel (A1A2 mode) 210-1 10'b111111111 Serial or parallel (10-bit mode) Incremental 10'b0011111010 Serial or parallel or post (10-bit mode) 8B/10B parallel
8–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Built-In Self Test (BIST)
Design The purpose of these design examples are to show how to instantiate and operate the various BIST modes in Stratix GX devices. The following Examples reference designs cover:
■ PRBS BIST generator and verification design ■ Incremental BIST generator and verification design ■ High-frequency transmitter generation design ■ Low-frequency transmitter generation design ■ Mixed-frequency transmitter generation design
Design 1: PRBS BIST Generator & Verification Design
This design shows how to use the BIST in PRBS 210-1 mode. You can also apply this design principle to the 28-1 by changing the data-width mode, comma, and word-alignment mode as listed in Table 8–2 on page 8–6.
A useful circuit to include in the PRBS verifier is a self-timed reset controller. This controller prevents bounce conditions that might occur when an external switch is used. This design consists of a reset module (reset.v) that periodically toggles the rxdigitalreset signal of the altgxb instantiation (PRBS_BIST.v). Figure 8–3 shows a block diagram of this design.
Figure 8–3. Block Diagram of the PRBS BIST Design
rx_in PRBS_BIST inclk[0] tx_out[0] tx_out rx_in[0] coreclk_out[0] coreclk_out reset_mod rx_slpbk[0] rx_clkout[0] rx_clkout inclk clk reset rxdigitalreset[0] rx_bistdone[0] rx_bistdone reset_mod_inst rx_bisterr[0] rx_bisterr PRBS_BIST_inst
reset
Top-Level Design (PRBS.v) module PRBS( inclk, rx_in, coreclk_out, tx_out, rx_bisterr, rx_bistdone, rx_clkout, reset );
Altera Corporation 8–7 January 2005 Stratix GX Transceiver User Guide Design Examples
input inclk; input rx_in; output coreclk_out; output tx_out; output rx_bisterr; output rx_bistdone; output rx_clkout; output reset;
wire reset_wire; wire VCC; assign reset = reset_wire; assign VCC = 1;
//Altgxb Instantiation////////////////////////////
PRBS_BIST PRBS_BIST_inst( .inclk(inclk), .rx_in(rx_in), .rx_slpbk(VCC), .rxdigitalreset(reset_wire), .coreclk_out(coreclk_out), .rx_bistdone(rx_bistdone), .rx_bisterr(rx_bisterr), .rx_clkout(rx_clkout), .tx_out(tx_out));
//Reset Module Instantiation//////////////////
reset_mod reset_mod_inst( .clk(inclk), .reset(reset_wire)); endmodule
Reset Module Design (reset_mod.v) module reset_mod(clk, reset); input clk; output reset; reg [19:0] counter; reg reset;
always @ (posedge clk) counter = counter +1; always @ (counter) begin if ((counter >= 20'b11111111111111100000) && (counter <= 20'b11111111111111111111)) reset = 1'b1; else reset = 1'b0; end
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endmodule
altgxb Instantiation (PRBS_BIST.v) module PRBS_BIST ( inclk, rx_in, rx_slpbk, rxdigitalreset, tx_out, coreclk_out, rx_clkout, rx_bistdone, rx_bisterr);
input[ 0:0] inclk; input[ 0:0] rx_in; input [0:0] rx_slpbk; input [0:0] rxdigitalreset; output [0:0] tx_out; output [0:0] coreclk_out; output [0:0] rx_clkout; output [0:0] rx_bistdone; output [0:0] rx_bisterr;
wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] sub_wire2; wire [0:0] sub_wire3; wire [0:0] sub_wire4; wire [0:0] tx_out = sub_wire0[0:0]; wire [0:0] coreclk_out = sub_wire1[0:0]; wire [0:0] rx_clkout = sub_wire2[0:0]; wire [0:0] rx_bistdone = sub_wire3[0:0]; wire [0:0] rx_bisterr = sub_wire4[0:0];
altgxbaltgxb_component (
.inclk (inclk), .rx_in (rx_in), .rx_slpbk (rx_slpbk), .rxdigitalreset (rxdigitalreset),
Altera Corporation 8–9 January 2005 Stratix GX Transceiver User Guide Design Examples
.tx_out (sub_wire0), .coreclk_out (sub_wire1), .rx_clkout (sub_wire2), .rx_bistdone (sub_wire3), .rx_bisterr (sub_wire4));
defparam altgxb_component.force_disparity_mode = "OFF", altgxb_component.channel_width = 20, altgxb_component.pll_inclock_period = 6400, altgxb_component.use_symbol_align = "ON", altgxb_component.rx_ppm_setting = 1000, altgxb_component.pll_bandwidth_type = "LOW", altgxb_component.dwidth_factor = 2, altgxb_component.number_of_channels = 1, altgxb_component.vod_ctrl_setting = 1000, altgxb_component.align_pattern_length = 10, altgxb_component.use_self_test_mode = "ON", altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON", altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.equalizer_ctrl_setting = 0, altgxb_component.use_auto_bit_slip = "ON", altgxb_component.use_rate_match_fifo = "OFF", altgxb_component.signal_threshold_select = 80, altgxb_component.self_test_mode = 0, altgxb_component.use_double_data_mode = "ON", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "CUSTOM", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.rx_bandwidth_type = "LOW", altgxb_component.disparity_mode = "ON", altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.loopback_mode = "SLB", altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.use_equalizer_ctrl_signal = "OFF", altgxb_component.rx_enable_dc_coupling = "OFF", altgxb_component.run_length_enable = "OFF", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "DUPLEX", altgxb_component.use_8b_10b_mode = "OFF", altgxb_component.use_rx_clkout = "ON", altgxb_component.data_rate_remainder = 0,
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altgxb_component.data_rate = 3125, altgxb_component.align_pattern = "P1111111111", altgxb_component.use_rx_cruclk = "OFF",
altgxb_component.number_of_quads = 1;
endmodule
Results A quick method for verifying whether the BIST verification passes or fails is to use the SignalTap® II logic analyzer in the Quartus® II software. Refer to Application Note 280: Design Verification Using the SignalTap II Logic Analyzer for more information on using the SignalTap II logic analyzer. The SignalTap II logic analyzer trigger is set to the falling edge of the reset output signal. Figure 8–4 is a screen shot of the SignalTap II logic analyzer results for this PRBS BIST test.
Figure 8–4. SignalTap II Logic Analyzer Results for PRBS BIST Test Design
(2) (3)
(1)
rx_bisterr remains low, signifying no bit errors Resets the Verifier rx_bistdone signifies that the verification cycle is complete
Design 2: Incremental BIST Generator & Verification Design
This design is similar to the PRBS BIST generator and verification design, except the altgxb megafunction is configured to the incremental BIST mode. Refer to the design for information on the ports and parameters required for altgxb in this mode.
As in the PRBS design, a useful circuit to include in the PRBS verifier is a self-timed reset controller. This controller prevents bounce conditions that might occur when an external switch is used. This design consists of a reset module (reset.v) that periodically toggles the rxdigitalreset signal of the altgxb instantiation (Incremental_BIST.v). Figure 8–5 shows a block diagram of this design.
Altera Corporation 8–11 January 2005 Stratix GX Transceiver User Guide Design Examples
Figure 8–5. Block Diagram of the Incremental BIST Design
rx_in Incr_BIST inclk[0] tx_out[0] tx_out rx_in[0] coreclk_out[0] coreclk_out reset_mod rx_slpbk[0] rx_clkout[0] rx_clkout inclk clk reset rxdigitalreset[0] rx_bistdone[0] rx_bistdone reset_mod_inst rx_bisterr[0] rx_bisterr Incr_BIST_inst
reset
Top-Level Design (Incremental) module incremental( inclk, rx_in,
coreclk_out, tx_out, rx_bisterr, rx_bistdone, rx_clkout, reset
);
input inclk; input rx_in; outputcoreclk_out; output tx_out; outputrx_bisterr; output rx_bistdone; output rx_clkout; output reset;
wire reset_wire; wire VCC;
assign reset = reset_wire; assign VCC = 1; Incr_BIST Incr_BIST_inst( .inclk(inclk), .rx_in(rx_in), .rx_slpbk(VCC), .rxdigitalreset(reset_wire),
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.coreclk_out(coreclk_out), .rx_bistdone(rx_bistdone), .rx_bisterr(rx_bisterr), .rx_clkout(rx_clkout), .tx_out(tx_out));
reset_mod reset_mod_inst( .clk(inclk), .reset(reset_wire));
endmodule
Reset Module Design (reset_mod.v) module reset_mod(clk, reset); input clk; output reset;
reg [19:0] counter;
reg reset;
always @ (posedge clk) counter = counter +1;
always @ (counter) begin if ((counter >= 20'b11111111111111100000) && (counter <= 20'b11111111111111111111)) reset = 1'b1; else reset = 1'b0; end
endmodule
altgxb Instantiation (Incr_BIST.v) module Incr_BIST ( inclk, rx_in, rx_slpbk, rxdigitalreset, tx_out, coreclk_out, rx_clkout, rx_bistdone, rx_bisterr);
Altera Corporation 8–13 January 2005 Stratix GX Transceiver User Guide Design Examples
input [0:0] inclk; input [0:0] rx_in; input [0:0] rx_slpbk; input [0:0] rxdigitalreset; output [0:0] tx_out; output [0:0] coreclk_out; output [0:0] rx_clkout; output [0:0] rx_bistdone; output [0:0] rx_bisterr;
wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] sub_wire2;
wire [0:0] sub_wire3; wire [0:0] sub_wire4; wire [0:0] tx_out = sub_wire0[0:0]; wire [0:0] coreclk_out = sub_wire1[0:0]; wire [0:0] rx_clkout = sub_wire2[0:0]; wire [0:0] rx_bistdone = sub_wire3[0:0]; wire [0:0] rx_bisterr = sub_wire4[0:0];
altgxb altgxb_component ( .inclk (inclk), rx_in (rx_in), .rx_slpbk (rx_slpbk), .rxdigitalreset (rxdigitalreset), .tx_out (sub_wire0), .coreclk_out (sub_wire1), .rx_clkout (sub_wire2), .rx_bistdone (sub_wire3), .rx_bisterr (sub_wire4));
defparam
altgxb_component.force_disparity_mode = "OFF", altgxb_component.channel_width = 16, altgxb_component.pll_inclock_period = 6250, altgxb_component.use_symbol_align = "ON", altgxb_component.rx_ppm_setting = 1000, altgxb_component.pll_bandwidth_type = "LOW", altgxb_component.dwidth_factor = 2, altgxb_component.number_of_channels = 1, altgxb_component.vod_ctrl_setting = 1000, altgxb_component.align_pattern_length = 10, altgxb_component.use_self_test_mode = "ON",
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altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON", altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.equalizer_ctrl_setting = 0, altgxb_component.use_auto_bit_slip = "ON", altgxb_component.use_rate_match_fifo = "OFF", altgxb_component.signal_threshold_select = 80, altgxb_component.self_test_mode = 1, altgxb_component.use_double_data_mode = "ON", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "CUSTOM", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.rx_bandwidth_type = "LOW", altgxb_component.disparity_mode = "ON", altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.loopback_mode = "SLB", altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.use_equalizer_ctrl_signal = "OFF", altgxb_component.rx_enable_dc_coupling = "OFF", altgxb_component.run_length_enable = "OFF", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "DUPLEX", altgxb_component.use_8b_10b_mode = "ON", altgxb_component.use_rx_clkout = "ON", altgxb_component.data_rate_remainder = 0, altgxb_component.data_rate = 2560, altgxb_component.align_pattern = "P0011111010", altgxb_component.use_rx_cruclk = "OFF", altgxb_component.number_of_quads = 1;
endmodule
Results A quick method for verifying whether the BIST verification passes or fails is to use the SignalTap II embedded logic analyzer in the Quartus II software. Refer to Application Note 280: Design Verification Using the SignalTap II Logic Analyzer for more information. The SignalTap II trigger is set to the falling edge of the reset output signal. Figure 8–6 is a screen shot of the SignalTap II results for the incremental BIST results.
Altera Corporation 8–15 January 2005 Stratix GX Transceiver User Guide Design Examples
Figure 8–6. SignalTap II Results for PRBS BIST Test Design (Resets the Verifier)
(2)
(3) (1)
rx_bistdone signifies that the rx_bisterr remains low, resets the verifier verification cycle is complete signifying no bit errors
Design 3: High-Frequency Transmitter Generator Design
This design shows how to instantiate the altgxb megafunction in the high-frequency BIST mode. Because this design consists only of a single transmitter design, only the altgxb instantiation is shown. The top level simply consists of calling the megafunction instance.
altgxb Instantiation (High_Freq_BIST.v) module high_freq_BIST ( inclk, tx_out, coreclk_out);
input [ 0:0] inclk; output [0:0] tx_out; output [0:0] coreclk_out;
wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] tx_out = sub_wire0[0:0]; wire [0:0] coreclk_out = sub_wire1[0:0];
altgxb altgxb_component (
.inclk (inclk), .tx_out (sub_wire0), .coreclk_out (sub_wire1));
defparam
altgxb_component.force_disparity_mode = "OFF", altgxb_component.channel_width = 16,
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altgxb_component.pll_inclock_period = 6250, altgxb_component.pll_bandwidth_type = "LOW" , altgxb_component.dwidth_factor = 2, altgxb_component.number_of_channels = 1 , altgxb_component.vod_ctrl_setting = 1000, altgxb_component.use_self_test_mode = "ON", altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON", altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.self_test_mode = 2, altgxb_component.use_double_data_mode = "ON", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "CUSTOM", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "TX", altgxb_component.use_8b_10b_mode = "ON", altgxb_component.use_rx_clkout = "OFF", altgxb_component.data_rate_remainder = 0, altgxb_component.data_rate = 2560, altgxb_component.use_rx_cruclk = "OFF", altgxb_component.number_of_quads = 1;
endmodule
Results Figure 8–7 shows a screen shot of the high-frequency BIST mode. The signal was captured using a sampling oscilloscope.
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Figure 8–7. High-Frequency BIST Measured on tx_out[]
Design 4: Low-Frequency Transmitter Generator Design
This design shows how to instantiate the altgxb megafunction in the low-frequency BIST mode. Because this design consists only of a single transmitter design, only the altgxb instantiation is shown. The top level simply consists of calling the megafunction instance.
altgxb Instantiation (low_freq_BIST.v) module low_freq_BIST ( inclk, tx_out, coreclk_out);
input [0:0] inclk;
output [0:0] tx_out; output [0:0] coreclk_out;
wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] tx_out = sub_wire0[0:0]; wire [0:0] coreclk_out = sub_wire1[0:0];
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altgxb altgxb_component ( inclk (inclk), .tx_out (sub_wire0), .coreclk_out (sub_wire1));
defparam altgxb_component.force_disparity_mode = "OFF", altgxb_component.channel_width = 16, altgxb_component.pll_inclock_period = 6250, altgxb_component.pll_bandwidth_type = "LOW", altgxb_component.dwidth_factor = 2, altgxb_component.number_of_channels = 1, altgxb_component.vod_ctrl_setting = 1000, altgxb_component.use_self_test_mode = "ON", altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON", altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.self_test_mode = 3, altgxb_component.use_double_data_mode = "ON", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "CUSTOM", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "TX", altgxb_component.use_8b_10b_mode = "ON", altgxb_component.use_rx_clkout = "OFF", altgxb_component.data_rate_remainder = 0, altgxb_component.data_rate = 2560, altgxb_component.use_rx_cruclk = "OFF", altgxb_component.number_of_quads = 1;
endmodule
Results The low-frequency BIST mode is shown in Figure 8–8. The signal was captured using a sampling oscilloscope.
Altera Corporation 8–19 January 2005 Stratix GX Transceiver User Guide Design Examples
Figure 8–8. Low-Frequency BIST Measured on tx_out[]
Design 5: Mix-Frequency Transmitter Generator Design
The mix-frequency transmitter generator design shows how to instantiate the altgxb megafunction in the mix-frequency BIST mode. Because this design consists only of a single transmitter design, only the altgxb instantiation is shown. The top level simply consists of calling the megafunction instance.
altgxb Instantiation (mix_freq_BIST.v) module mix_freq_BIST ( inclk, tx_out, coreclk_out);
input [0:0] inclk; output[0:0] tx_out; output[0:0] coreclk_out;
wire [0:0] sub_wire0; wire [0:0] sub_wire1; wire [0:0] tx_out = sub_wire0[0:0]; wire [0:0] coreclk_out = sub_wire1[0:0];
8–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 Stratix GX Built-In Self Test (BIST)
altgxb altgxb_component ( inclk (inclk), .tx_out (sub_wire0), .coreclk_out (sub_wire1));
defparam altgxb_component.force_disparity_mode = "OFF", altgxb_component.channel_width = 16, altgxb_component.pll_inclock_period = 6250, altgxb_component.pll_bandwidth_type = "LOW", altgxb_component.dwidth_factor = 2, altgxb_component.number_of_channels = 1, altgxb_component.vod_ctrl_setting = 1000, altgxb_component.use_self_test_mode = "ON", altgxb_component.lpm_type = "altgxb", altgxb_component.use_fifo_mode = "ON",
altgxb_component.use_vod_ctrl_signal = "OFF", altgxb_component.self_test_mode = 4, altgxb_component.use_double_data_mode = "ON", altgxb_component.use_preemphasis_ctrl_signal = "OFF", altgxb_component.protocol = "CUSTOM", altgxb_component.clk_out_mode_reference = "ON", altgxb_component.preemphasis_ctrl_setting = 0, altgxb_component.use_channel_align = "OFF", altgxb_component.intended_device_family = "Stratix GX", altgxb_component.pll_use_dc_coupling = "OFF", altgxb_component.operation_mode = "TX", altgxb_component.use_8b_10b_mode = "ON", altgxb_component.use_rx_clkout = "OFF", altgxb_component.data_rate_remainder = 0, altgxb_component.data_rate = 2560, altgxb_component.use_rx_cruclk = "OFF", altgxb_component.number_of_quads = 1;
endmodule
Results Figure 8–9 shows a screen shot of the mix-frequency BIST mode. The signal was captured using a sampling oscilloscope.
Altera Corporation 8–21 January 2005 Stratix GX Transceiver User Guide Design Examples
Figure 8–9. Mix-Frequency BIST Measured on tx_out[]
8–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 9. Reset Control & Power Down
Introduction Stratix® GX transceivers offer multiple reset signals to control separate ports of the transceiver channels and transceiver blocks, as shown in Figure 9–1. The Quartus® II software sets each unused channel to a power-down mode to reduce power consumption.
Figure 9–1. Reset Control Diagram
txdigitalreset
rxdigitalreset Reset rxanalogreset Control pll_areset
pllenable
Power On Reset At power on, the Stratix GX transceiver uses built-in circuits that handle the reset of the digital and analog circuits. After power on reset (POR), the (POR) Stratix GX block is guaranteed to be in a known state.
USER Reset & Each transceiver block and channel in the Stratix GX transceiver block has individual reset signals to reset the digital and analog portions of the Enable Signals channel. The txdigitalreset, rxdigitalreset, and rxanalogreset signals affect the channels individually. The pll_areset and pllenable signals affect the entire transceiver block.
The pll_areset signal is a power-down signal and powers down the entire transceiver block. The analog circuitry is powered down when the pll_areset signal goes high. Although there is no specific requirement on the duration of the pll_areset signal, Altera® lab experiments have shown that 1 ms is a safe value. If you use the pll_areset signal to power down the analog circuitry, Altera recommends that you use the pll_locked and rx_freqlocked signals from the transceiver block to implement your reset logic.
Altera Corporation 9–1 January 2005 USER Reset & Enable Signals
The rxanalogreset signal is a power-down signal and only powers down the receiver. The analog circuitry is powered down when the rxanalogreset signal goes high. Although there is no specific requirement on the duration of the rxanalogreset signal, Altera lab experiments have shown that 1 ms is a safe value. If you use the rxanalogreset signal to power down the analog circuitry, Altera recommends that you use the rx_freqlocked signal from the receiver block to implement your reset logic.
The rxdigitalreset signal resets the digital logic in the receiver section of the transceiver block. This signal is synchronized within the transceiver block. The minimum duration required on the rxdigitalreset signal is four parallel clock cycles.
The txdigitalreset signal resets the digital logic in the transmitter section of the transceiver block. This signal is synchronized within the transceiver block. The minimum duration required on the txdigitalreset signal is four parallel clock cycles.
f If you use REFCLKB pins in your design, refer to Appendix C, REFCLKB Pin Constraints for analog reset (pll_areset, rxanalogreset, pll_enable) refclkb usage constraints.
You do not have to use all of the reset and enable signals. If the reset and power-down signals are not used, they default to their inactive levels.
Under normal operating conditions, you do not have to power down the transmitter PLL. The PLLs should only be powered down as the last option because there is a significant delay to recover from a power down state and return to normal operation.
If the read and write pointers in the phase compensation FIFO buffers point to the same location, the buffer outputs incorrect data. This can occur during system initialization. If this occurs, use the digital reset signals (rxdigitalreset and txdigitalreset) to reset the digital logic of that channel.
Table 9–1 shows the reset and enable signals that are required for the transceiver blocks.
9–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
In 16-bit or 20-bit mode, asserting rxdigitalreset causes the recovered clock or the slow clock to reset. The slow clock is divided down by the deserialization factor from rx_clkout. Altera recommends synchronizing rxdigitalreset to the FPGA or the logic array clock.
Table 9–1. Reset Signal Map to Stratix GX Blocks FIFO Module/ Byte Serializer FIFO FO Module/ Byte Deserializer FO BIST Verifiers Transmitter PLL Transmitter BIST Generators Receiver PLL / CRU Receiver Receiver Deserializer Receiver Transmitter Serializer Transmitter Receiver Word Aligner Receiver Word Receiver Rate Matcher Receiver Analog Circuits Receiver 8B/10B Decoder Receiver Transmitter Analog Circuits Analog Transmitter Circuits Analog Transmitter Transmitter 8B/10B Encoder Transmitter Receiver XAUI State Machine Receiver Deskew FIFO Module Deskew Receiver Transmitter XAUI State Machine Transmitter Receiver Phase Compensation FI Receiver Phase Compensation Transmitter Phase Compensation Phase Transmitter rxdigitalreset vvvvv vv
rxanalogreset vvv
txdigitalreset vv v v
pll_areset vvvvvvvvvvvvvvvvvv
pllenable vvvvvvvvvvvvvvvvvv
Link initialization must be performed after any reset condition. You must determine when the data is valid after reset (for example, by using the rx_syncstatus signal in XAUI mode).
Altera Corporation 9–3 January 2005 Stratix GX Transceiver User Guide Recommended Resets
Recommended The following reset recommendations help guard against potential initialization issues during the training of the transmitter PLL and Resets receiver PLLs. The counters that you specify in the recommendations filter out any high frequency effects to ensure that the lock signals are stable before releasing the subsequent reset signals. This action adds to the robustness of the reset sequence.
Receiver & Transmitter Reset
The configurations and design examples in this section describe how to implement a reset sequence for both the receiver and transmitter channels. The designs in this section demonstrate the reset sequence only. Each design example lists the constraints specific to the example to help you understand the design parameters and limitations. You may want to add additional escape states and other system-specific features in your design. If your design requirements and GXB configurations are different (for example, usage for multiple transceivers) from the design example, you can make necessary changes using the flow chart and waveform figures in each section as guidelines.
Train Receive CRU With Transmit PLL Output Clock This section contains RTL examples that show some scenarios where a transceiver is programmed to duplex and the transmitter PLL output clock trains the receiver clock recovery unit (CRU).
Figure 9–2 shows the possible options on clocking the transmit and receive parallel interface for a selected data path width.
Figure 9–2. Receiver & Transmitter Clock Options
Transmit & Receive (Duplex) with Train RX CRU with TXPLL Output Clock Data Path Width
Single Width Double Width (8/10) (16/20)
Receive Transmit Receive Transmit Parallel Clock Parallel Clock Parallel Clock Parallel Clock
rx_clkout rx_coreclk tx_coreclk inclk rx_clkout tx_coreclk inclk
9–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Figure 9–3 shows a situation in which you must reset both the transmitter and receiver channels.
Figure 9–3. Receiver & Transmitter Reset Sequence
async_reset or sync_reset
Start
pll_areset = high pll_areset = low rxanalogreset = high rxanalogreset = low txdigitalreset = high txdigitalreset = low rxdigitalreset = high rxdigitalreset = high wait_state
pll_areset = low rxanalogreset = high waitstate_timer NO txdigitalreset = high = 0? rxdigitalreset = high
YES
pll_areset = low pll_locked NO rxanalogreset = low = high? txdigitalreset = low rxdigitalreset = low
YES
NO pll_areset = low rxanalogreset = low transmit_digitalreset receive_digitalreset txdigitalreset = low = high = high rxdigitalreset = high
YES YES
txdigitalreset rxdigitalreset = high = high NOrx_freqlocked = YES high?
Altera Corporation 9–5 January 2005 Stratix GX Transceiver User Guide Recommended Resets
The waveform in Figure 9–4 shows the functionality of the receiver and transmitter reset sequence shown in Figure 9–3. The pll_areset signal resets the entire transceiver block, including both the analog and digital portions of the transmitter and receiver (see Table 9–1). After the pll_areset signal goes low, the controller waits until the transmitter PLL is stable (pll_locked = 1’b1) before sending the tx_digitalreset and rx_analogreset low. This ensures that the output of the transmitter PLL is stable before releasing any of the logic that it feeds. The transmitter PLL clock in this case also trains the receiver PLL. After the CRU has transitioned to locking to data from locking to the reference clock, the rx_freqlocked signal goes high, which allows the CRU to transition into the wait state where a timer is loaded a certain amount of time. See the Stratix GX FPGA Family data sheet for the amount of time loaded into the timer. When the timer counts down, rx_clkout is stable. The reset controller then sends rx_digital low, completing the reset sequence. You will be able to monitor the BER (for example, a synchronization state machine based on the Stratix GX transceiver data) to determine whether the system is initialized and working properly.
Figure 9–4. Receiver & Transmitter Reset Sequence Waveforms
Reset Signals pll_areset
tx_digitalreset
rx_analogreset
rx_digitalreset Stable Transmit Pll Clock
Output Status Signals
Stable Recovered Clock pll_locked
rx_freqlocked
Trx_freqlock2phaselock
9–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Design Example 1 This design example shows inclk as the input reference clock and the transmit parallel clock and rx_coreclk as the receive parallel clock. The design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation ======
We have made every effort to ensure that this design example works correctly. If you have a question or problem that is not answered by the information then please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Both used Datapath : Single Width(8/10 bits) receive parallel clock: rx_coreclk Functional Mode :'Any' RX PLL CRU : Train RX PLL CRU with TX PLL ouput clock ***************************************************************/
`timescale 1ns/10ps
module reset_seq_tx_train_rx_rx_coreclk ( rx_coreclk, inclk,
sync_reset, async_reset, transmit_digitalreset,
Altera Corporation 9–7 January 2005 Stratix GX Transceiver User Guide Recommended Resets
receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, txdigitalreset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_coreclk;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input transmit_digitalreset; //Input: Reset only the transmit digital section input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal output txdigitalreset; //GXB transmit digital reset output pll_areset;//GXB power down signal
reg rxdigitalreset; wire rxanalogreset; reg txdigitalreset; reg pll_areset; reg [2:0] state; reg rxdigitalreset_inclk; reg rxanalogreset_inclk;
reg rxdigitalreset_rx_coreclk_Q; reg rxanalogreset_rx_coreclk_Q;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001; parameter STABLE_TX_PLL = 3'b010; parameter WAIT_STATE = 3'b011;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
assign rxanalogreset = rxanalogreset_inclk;
9–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STROBE_TXPLL_LOCKED;
end else begin rxdigitalreset_inclk <= 1'b0; rxanalogreset_inclk <= 1'b0; pll_areset <= 1'b0; state <= IDLE; if(transmit_digitalreset) txdigitalreset <= 1'b1; else txdigitalreset <= 1'b0; end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin
Altera Corporation 9–9 January 2005 Stratix GX Transceiver User Guide Recommended Resets
state <= STROBE_TXPLL_LOCKED; rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if (rx_freqlocked) begin state <= WAIT_STATE; waitstate_timer <= waitstate_timer - 1'b1 ; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end WAIT_STATE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if(rx_freqlocked) //Condition to have rx_freqlocked signal a stable high and should not bounce around begin //Decrement a Timer of 2ms (Refer Stratix GX Datasheet for accurate value)after rx_freqlocked is asserted //This time is given to ensure the recovered clock to be stable (No freq variations) and is locked to incomming data if(waitstate_timer == 0) begin state <= IDLE; rxdigitalreset_inclk<= 1'b0; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0;
9–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
pll_areset <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; state <= WAIT_STATE; end end else begin rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STABLE_TX_PLL; end
default: state = IDLE; endcase end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is only used for Receive GXB, then synchronization is needed because internally the rxdigitalreset is only synchronized to recovered clock (rx_clkout). In the above description of the module, a typical user likes to operate on the system clock or PLD clock domain. To reset the rx_coreclk domain logic in PLD fabric following reset is useful */
/* rxanalogreset is optional because it is a power down signal. The longer the duration of assertion of power down signal, the circuit will go into a true power down state */ always @(posedge rx_coreclk or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1; end
Altera Corporation 9–11 January 2005 Stratix GX Transceiver User Guide Recommended Resets
else begin rxdigitalreset_rx_coreclk_Q <= rxdigitalreset_inclk; rxdigitalreset <= rxdigitalreset_rx_coreclk_Q; end end
endmodule
Design Example 2 The following design example shows inclk as the input reference clock and the transmit parallel clock and rx_clkout as the receive parallel clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example contains an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question or problem that is not answered by the information then please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is:
9–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Transmit and Receive : Both used Datapath : Single Width(8/10 bits) or Double Width (16/20 bits) receive parallel clock: rx_clkout Functional Mode :'Any' RX PLL CRU : Train RX PLL CRU with TX PLL ouput clock
***************************************************************/
`timescale 1ns/10ps
module reset_seq_tx_train_rx_rx_clkout ( rx_clkout, inclk,
sync_reset, async_reset, transmit_digitalreset, receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, txdigitalreset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_clkout;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input transmit_digitalreset; //Input: Reset only the transmit digital section input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal output txdigitalreset; //GXB transmit digital reset output pll_areset;//GXB power down signal
reg rxdigitalreset; wire rxanalogreset; reg txdigitalreset; reg pll_areset; reg [2:0] state; reg rxdigitalreset_inclk; reg rxanalogreset_inclk;
Altera Corporation 9–13 January 2005 Stratix GX Transceiver User Guide Recommended Resets
reg rxdigitalreset_rx_clkout_Q; reg rxanalogreset_rx_clkout_Q;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001; parameter STABLE_TX_PLL = 3'b010; parameter WAIT_STATE = 3'b011;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
assign rxanalogreset = rxanalogreset_inclk;
always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state<= STROBE_TXPLL_LOCKED;
end else begin rxdigitalreset_inclk <= 1'b0; rxanalogreset_inclk <= 1'b0; pll_areset <= 1'b0; state <= IDLE; if(transmit_digitalreset) txdigitalreset <= 1'b1; else txdigitalreset <= 1'b0; end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished)
9–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin state <= STROBE_TXPLL_LOCKED; rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if (rx_freqlocked) begin state <= WAIT_STATE; waitstate_timer <= waitstate_timer - 1'b1 ; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end WAIT_STATE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; txdigitalreset <= 1'b1;
Altera Corporation 9–15 January 2005 Stratix GX Transceiver User Guide Recommended Resets
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if(rx_freqlocked) //Condition to have rx_freqlocked signal a stable high and should not bounce around begin //Decrement a Timer of 2ms (Refer Stratix GX Datasheet for accurate value)after rx_freqlocked is asserted //This time is given to ensure the recovered clock to be stable (No freq variations) and is locked to incomming data if(waitstate_timer == 0) begin state <= IDLE; rxdigitalreset_inclk<= 1'b0; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; state<= WAIT_STATE; end end else begin rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0; txdigitalreset<= 1'b0; pll_areset <= 1'b0; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STABLE_TX_PLL; end
default: state = IDLE; endcase end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is only used for Receive GXB, then this synchronization is redundant because internally the rxdigitalreset is synchronized to recovered clock (rx_clkout). In the above description of the module, a typical designer likes to operate on the system clock or PLD clock domain where one would like to have a FIFO with rx_clkout domain being write clock and
9–16 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
pld clock domain(Generic name, can be any clock name) as read clock. To reset the rx_clkout domain logic in PLD fabric following reset is useful */
always @(posedge rx_clkout or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_clkout_Q <= rxdigitalreset_inclk; rxdigitalreset <= rxdigitalreset_rx_clkout_Q; end end
endmodule
Train Receive CRU With Transmit PLL Output Clock Option Disabled The configuration in this section is similar to having two independent transmit and receive PLLs with their respective input reference clocks (inclk and rx_cruclk). In this configuration, both the transmit and receive parts of the transceiver are used. Figure 9–5 shows the possible clock options for the selected transceiver configuration.
Altera Corporation 9–17 January 2005 Stratix GX Transceiver User Guide Recommended Resets
Figure 9–5. Receiver & Transmitter With No Train Receiver CRU Option
Transmit and Receive (Duplex) with Train RX CRU with TXPLL output clock option disabled
data path width Receive Parallel Clock Single Width Double Width (8/10) (16/20) Transmit Transmit Parallel Parallel Receive Clock Clock Parallel Clock
rx_clkout rx_coreclk tx_coreclk inclkrx_clkout tx_coreclk inclk
Figure 9–6 shows the transmitter reset sequence.
9–18 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Figure 9–6. Transmitter Reset Sequence
Start
async_reset or sync_reset
pll_areset = high txdigitalreset = high
pll_areset = low txdigitalreset = high
NO pll_locked = high pll_areset = low txdigitalreset = high
YES
YES
pll_areset = low transmit_digitalreset = high txdigitalreset = low NO
The waveform in Figure 9–7 shows the functionality of the transmitter reset sequence shown in Figure 9–6. As described in Table 9–1 on page 9–3, the pll_areset resets the entire transceiver block, including both the analog and digital portions of the transmitter and receiver. After this signal is deasserted, the controller waits until the transmitter PLL is stable (pll_locked = 1'b1) before deasserting tx_digitalreset. This ensures that the output of the transmitter PLL is stable before releasing any of the logic that it feeds.
Altera Corporation 9–19 January 2005 Stratix GX Transceiver User Guide Recommended Resets
Figure 9–7. Transmitter Reset Sequence Waveform
Reset Signals 12
pll_areset
4 tx_digitalreset
Stable TXPLL Clock Output Status 3
pll_locked
Figure 9–8 shows the receiver reset sequence.
9–20 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Figure 9–8. Receiver Reset Sequence
Start
pll_areset or sync_reset
rxanologreset = high rxdigitalreset = high
rxanalogreset = low rxanalogreset = low rxdigitalreset = high rxdigitalreset = low NO
receive_digitalreset = high
NO YES rxfreqlocked = high
rxanalogreset = low rxdigitalreset = high
YES rxanalogreset = low rxdigitalreset = high
NO waitstate_timer = 0 YES
The waveform in Figure 9–9 shows the functionality of the receiver reset sequence shown in Figure 9–8. The rx_analogreset signal is pulsed. After the CRU has transitioned to locking to data from locking to the reference clock, the rx_freqlocked signal is asserted, which allows the reset sequence to transition into a wait state, where a timer is loaded with T ms. When the timer counts down the value, it signifies that rx_clkout is stable. The reset controller then deasserts the rx_digital reset, which completes the reset sequence. You should be able to monitor the BER (for example, a synchronization state machine based on the Stratix GX transceiver data) to determine whether the system is initialized and working properly.
f See the Stratix GX FPGA Family data sheet for the value of Trx_freqlock2phaselock.
Altera Corporation 9–21 January 2005 Stratix GX Transceiver User Guide Recommended Resets
Figure 9–9. Receiver Reset Sequence Waveform
Reset Signals 12
rx_analogreset
4
rx_digitalreset
Stable Recovered Clock Output Status 3
rx_freqlocked
Trx_freqlock2phaselock
Design Example 1 This design example shows inclk as the transmit PLL input reference clock and the transmit parallel clock, rx_cruclk as the receive CRU input reference clock, and rx_coreclk as the receive parallel clock.
This design example has following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
9–22 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Both used Datapath : Single Width(8/10 bits) receive parallel clock: rx_coreclk Functional Mode :'Any' RX PLL CRU : rx_cruclk ***************************************************************/
`timescale 1ns/10ps
module reset_seq_tx_rx_rx_cruclk_rx_coreclk ( rx_coreclk, inclk, rx_cruclk,
sync_reset, async_reset, transmit_digitalreset, receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, txdigitalreset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_cruclk; //Receive GXB input reference clock input rx_coreclk;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input transmit_digitalreset; //Input: Reset only the transmit digital section input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
Altera Corporation 9–23 January 2005 Stratix GX Transceiver User Guide Recommended Resets
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal output txdigitalreset; //GXB transmit digital reset output pll_areset;//GXB power down signal
reg rxdigitalreset; reg txdigitalreset; reg pll_areset; reg [2:0] state; reg rxdigitalreset_rx_cruclk;
reg rxdigitalreset_rx_coreclk_Q; reg rxanalogreset;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001; parameter STABLE_TX_PLL = 3'b010;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
//Transmit Reset Sequence always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state<= STROBE_TXPLL_LOCKED;
end else begin pll_areset <= 1'b0; state <= IDLE; if(transmit_digitalreset) txdigitalreset <= 1'b1; else txdigitalreset <= 1'b0; end
9–24 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else begin state <= STROBE_TXPLL_LOCKED; txdigitalreset <= 1'b1; pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else state <= IDLE; default: state = IDLE; endcase end
//Receive Reset Sequence always @(posedge rx_cruclk or posedge pll_areset) if(pll_areset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin if(sync_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk<= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin rxanalogreset <= 1'b0; if (rx_freqlocked) begin if(waitstate_timer == 0)
Altera Corporation 9–25 January 2005 Stratix GX Transceiver User Guide Recommended Resets
begin
waitstate_timer <= waitstate_timer; if(receive_digitalreset)
rxdigitalreset_rx_cruclk <= 1'b1; else
rxdigitalreset_rx_cruclk <= 1'b0; end else begin
waitstate_timer <= waitstate_timer - 1'b1; rxdigitalreset_rx_cruclk <= 1'b1; end end else begin rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end end end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is used for Receive GXB, then this synchronization is needed because internally the rxdigitalreset is only synchronized to recovered clock (rx_clkout). To reset the rx_coreclk domain logic in PLD fabric following reset is useful */
always @(posedge rx_coreclk or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_coreclk_Q <= rxdigitalreset_rx_cruclk; rxdigitalreset <= rxdigitalreset_rx_coreclk_Q;
9–26 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
end end
endmodule
Design Example 2 This design example shows inclk as the transmit PLL input reference clock and transmit parallel clock, rx_cruclk as the receive CRU input reference clock, and rx_clkout as the receive parallel clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Both used Datapath : Single Width(8/10 bits) or Double Width(16/20 bits) receive parallel clock: rx_clkout Functional Mode :'Any' RX PLL CRU : rx_cruclk
Altera Corporation 9–27 January 2005 Stratix GX Transceiver User Guide Recommended Resets
***************************************************************/
`timescale 1ns/10ps
module reset_seq_tx_rx_rx_cruclk_rx_clkout ( rx_clkout, inclk, rx_cruclk,
sync_reset, async_reset, transmit_digitalreset, receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, txdigitalreset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_cruclk; //Receive GXB input reference clock input rx_clkout;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input transmit_digitalreset; //Input: Reset only the transmit digital section input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal output txdigitalreset; //GXB transmit digital reset output pll_areset;//GXB power down signal
reg rxdigitalreset; reg txdigitalreset; reg pll_areset; reg [2:0] state; reg rxdigitalreset_rx_cruclk;
reg rxdigitalreset_rx_clkout_Q; reg rxanalogreset;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001;
9–28 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
parameter STABLE_TX_PLL = 3'b010;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
//Transmit Reset Sequence always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED;
end else begin pll_areset <= 1'b0; state <= IDLE; if(transmit_digitalreset) txdigitalreset <= 1'b1; else txdigitalreset <= 1'b0; end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; txdigitalreset<= 1'b0; pll_areset <= 1'b0; end else
Altera Corporation 9–29 January 2005 Stratix GX Transceiver User Guide Recommended Resets
begin state <= STROBE_TXPLL_LOCKED; txdigitalreset <= 1'b1; pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else state <= IDLE; default: state = IDLE; endcase end
//Receive Reset Sequence always @(posedge rx_cruclk or posedge pll_areset) if(pll_areset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin if(sync_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk<= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin rxanalogreset <= 1'b0; if (rx_freqlocked) begin if(waitstate_timer == 0) begin waitstate_timer <= waitstate_timer;
if(receive_digitalreset)
rxdigitalreset_rx_cruclk <= 1'b1; else
rxdigitalreset_rx_cruclk <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1;
9–30 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
rxdigitalreset_rx_cruclk <= 1'b1; end end else begin
rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end end end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is only used for Receive GXB, then the following synchronization is not needed because internally the rxdigitalreset is synchronized to recovered clock (rx_clkout). In the above description of the module, a typical designer likes to operate on the system clock or PLD clock domain where one would like to have a FIFO with rx_clkout domain being write clock and may have pld clock domain(Generic name, can be any clock name) as read clock. pld clock is optional. To reset the rx_clkout domain logic in PLD fabric following reset is useful */
always @(posedge rx_clkout or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_clkout_Q <= rxdigitalreset_rx_cruclk; rxdigitalreset <= rxdigitalreset_rx_clkout_Q; end end
endmodule
Altera Corporation 9–31 January 2005 Stratix GX Transceiver User Guide Recommended Resets
Receiver Reset
The configurations and design examples in this section describe how to implement a reset sequence for the receiver channels. This section describes the reset sequence only. Each design example lists the constraints specific to the example to help you understand the design parameters and limitations. You may want to add additional escape states and other system-specific features in your design. If your design requirements are different from the design example, you can make necessary changes using the flow chart and waveform figures in each section as guidelines.
Receive CRU With Transmit PLL Output Clock Option Enabled This section provides some design examples that show a receive-only configuration with train receive CRU and the transmit PLL output clock enabled.
Figure 9–10 shows the receive-only clock options.
Figure 9–10. Receiver Only With Clock Options Enabled
Receive Only with Train RX CRU with TXPLL output clock option enabled
data path width
Single Width Double Width (8/10) (16/20)
Receive Parallel Clock Receive Parallel Clock
rx_clkout rx_coreclk rx_clkout
The flow chart in Figure 9–11 shows a situation where only the receive channel requires a reset sequence.
9–32 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Figure 9–11. Receiver Reset Sequence
Start
async_reset or sync_reset
pll_areset = high rxanologreset = high rxdigitalreset = high
pll_areset = low pll_areset = low rxanalogreset = low rxanalogreset = low rxdigitalreset = high rxdigitalreset = low NO
receive_digitalreset = high
NO YES rxfreqlocked = high
pll_areset = low rxanalogreset = low rxdigitalreset = high
YES pll_areset = low rxanalogreset = low rxdigitalreset = high
NO waitstate_timer = 0 YES
The waveform in Figure 9–12 shows the functionality of the receiver reset sequence shown in Figure 9–11. The rx_analogreset signal is pulsed. After the CRU has transitioned to locking-to-data from locking to the reference clock, the rx_freqlocked signal is asserted, which allows a reset sequence to transition into a wait state, where a timer is loaded with T ms. When the timer counts down the value, it signifies that rx_clkout is stable. The reset controller then deasserts the rx_digital reset, which completes the reset sequence.
Altera Corporation 9–33 January 2005 Stratix GX Transceiver User Guide Recommended Resets
f See the Stratix GX FPGA Family data sheet for the value of Trx_freqlock2phaselock.
Figure 9–12. Receiver Reset Sequence Waveform
Reset Signals 12
rx_analogreset
4
rx_digitalreset
Stable Recovered Clock Output Status 3
rx_freqlocked
Trx_freqlock2phaselock
Design Example 1 This design example shows a receive only configuration where inclk is the transmit PLL input reference clock, the output of transmit PLL trains receive CRU, and rx_coreclk is the receive parallel interface clock.
This design example has following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
9–34 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Receiver ONLY Datapath : Single Width(8/10 bits) or Double Width (16/20 bits) receive parallel clock: rx_coreclk Functional Mode :'Any' RX PLL CRU : Train RX PLL CRU with TX PLL ouput clock (refClk as shown in Mega Wizard)
***************************************************************/
`timescale 1ns/10ps
module reset_seq_rx_ONLY_TXPLL_rx_coreclk ( rx_coreclk, inclk,
sync_reset, async_reset, receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_coreclk;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system
input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
Altera Corporation 9–35 January 2005 Stratix GX Transceiver User Guide Recommended Resets
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal
output pll_areset;//GXB power down signal
reg rxdigitalreset; wire rxanalogreset;
reg pll_areset; reg [2:0] state; reg rxdigitalreset_inclk; reg rxanalogreset_inclk;
reg rxdigitalreset_rx_coreclk_Q; reg rxanalogreset_rx_coreclk_Q;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001; parameter STABLE_TX_PLL = 3'b010; parameter WAIT_STATE = 3'b011;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
assign rxanalogreset = rxanalogreset_inclk;
always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state<= STROBE_TXPLL_LOCKED;
end else
9–36 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
begin rxdigitalreset_inclk <= 1'b0; rxanalogreset_inclk <= 1'b0; pll_areset <= 1'b0; state <= IDLE;
end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin state <= STROBE_TXPLL_LOCKED; rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if (rx_freqlocked) begin state <= WAIT_STATE; waitstate_timer <= waitstate_timer - 1'b1 ; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1;
Altera Corporation 9–37 January 2005 Stratix GX Transceiver User Guide Recommended Resets
rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end WAIT_STATE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if(rx_freqlocked) //Condition to have rx_freqlocked signal a stable high and should not bounce around begin //Decrement a Timer of 2ms (Refer Stratix GX Datasheet for accurate value)after rx_freqlocked is asserted //This time is given to ensure the recovered clock to be stable (Cannot have any freq variations) and is locked to incomming data if(waitstate_timer == 0) begin state <= IDLE; rxdigitalreset_inclk<= 1'b0; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; state <= WAIT_STATE; end end else begin rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STABLE_TX_PLL; end
default: state = IDLE; endcase end
9–38 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is used for Receive GXB, then this synchronization is needed because internally the rxdigitalreset is synchronized to recovered clock (rx_clkout).To reset the rx_coreclk domain logic in PLD fabric following reset is useful */
always @(posedge rx_coreclk or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_coreclk_Q <= rxdigitalreset_inclk; rxdigitalreset <= rxdigitalreset_rx_coreclk_Q; end end
endmodule
Design Example 2 This design example shows a receive-only configuration where inclk is the transmit PLL input reference clock, the output of transmit PLL trains receive CRU, and rx_clkout is the receive parallel interface clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB.
Altera Corporation 9–39 January 2005 Stratix GX Transceiver User Guide Recommended Resets
■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information then please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Receiver ONLY Datapath : Single Width(8/10 bits) or Double Width (16/20 bits) receive parallel clock: rx_clkout Functional Mode :'Any' RX PLL CRU : Train RX PLL CRU with TX PLL ouput clock (refClk as shown in Mega Wizard)
***************************************************************/
`timescale 1ns/10ps
module reset_seq_rx_ONLY_TXPLL_rx_clkout ( rx_clkout, inclk,
sync_reset, async_reset, receive_digitalreset, pll_locked, rx_freqlocked,
pll_areset, rxanalogreset, rxdigitalreset
);
input inclk; //GXB input reference clock input rx_clkout;//Receive recovered clock
9–40 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system
input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode' input pll_locked; // Transmit PLL of GXB locked
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal
output pll_areset;//GXB power down signal
reg rxdigitalreset; wire rxanalogreset;
reg pll_areset; reg [2:0] state; reg rxdigitalreset_inclk; reg rxanalogreset_inclk;
reg rxdigitalreset_rx_clkout_Q; reg rxanalogreset_rx_clkout_Q;
parameter IDLE = 3'b000; parameter STROBE_TXPLL_LOCKED = 3'b001; parameter STABLE_TX_PLL = 3'b010; parameter WAIT_STATE = 3'b011;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
assign rxanalogreset = rxanalogreset_inclk;
always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1; pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1;
Altera Corporation 9–41 January 2005 Stratix GX Transceiver User Guide Recommended Resets
rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; state<= STROBE_TXPLL_LOCKED;
end else begin rxdigitalreset_inclk <= 1'b0; rxanalogreset_inclk <= 1'b0; pll_areset <= 1'b0; state <= IDLE;
end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU else if (pll_locked) begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin state <= STROBE_TXPLL_LOCKED; rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b0; end STABLE_TX_PLL: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if (rx_freqlocked) begin state <= WAIT_STATE;
9–42 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
waitstate_timer <= waitstate_timer - 1'b1 ; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin state <= STABLE_TX_PLL; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end WAIT_STATE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin rxdigitalreset_inclk <= 1'b1; rxanalogreset_inclk <= 1'b1;
pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else if(rx_freqlocked) //Condition to have rx_freqlocked signal a stable high and should not bounce around begin //Decrement a Timer of 2ms (Refer Stratix GX Datasheet for accurate value)after rx_freqlocked is asserted //This time is given to ensure the recovered clock to be stable (Cannot have any freq variations) and is locked to incomming data if(waitstate_timer == 0) begin state <= IDLE; rxdigitalreset_inclk<= 1'b0; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1; rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
pll_areset <= 1'b0; state <= WAIT_STATE; end end else begin rxdigitalreset_inclk<= 1'b1; rxanalogreset_inclk <= 1'b0;
Altera Corporation 9–43 January 2005 Stratix GX Transceiver User Guide Recommended Resets
pll_areset <= 1'b0; waitstate_timer <= WAITSTATE_TIMER_VALUE; state <= STABLE_TX_PLL; end
default: state = IDLE; endcase end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is only used for receive GXB, synchronization is redundant because internally the rxdigitalreset is synchronized to the recovered clock (rx_clkout). In the above description of the module, User likes to operate on the system clock or PLD clock domain where one would like to have a FIFO with rx_clkout domain being write clock and pld clock domain (generic name, can be any clock name) as read clock. To reset the rx_clkout domain logic in PLD fabric following reset is useful */
always @(posedge rx_clkout or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_clkout_Q <= rxdigitalreset_inclk; rxdigitalreset <= rxdigitalreset_rx_clkout_Q; end end
endmodule
Receive CRU With Transmit PLL Output Clock Option Disabled This section provides examples that show a receive-only configuration with a train receive CRU and the transmitter PLL output clock option disabled. The flow chart in Figure 9–11 on page 9–33 and the waveform shown in Figure 9–12 on page 9–34 are valid for this configuration also.
9–44 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
The difference in this configuration from the configuration in “Receive CRU With Transmit PLL Output Clock Option Enabled” on page 9–32 is that receive CRU is trained by the input pin rx_cruclk.
Figure 9–13 shows the receive-only configuration with clock options disabled.
Figure 9–13. Receive Clock Only With Clock Options Disabled
Receive Only with Train RX CRU with TXPLL Output Clock Option Disabled
data path width
Single Width Double Width (8/10) (16/20)
Receive Parallel Clock Receive Parallel Clock
rx_clkout rx_coreclk rx_clkout
Design Example 1 This design example shows a receive only configuration with rx_cruclk as the receive CRU input reference clock and rx_coreclk as the receive parallel interface clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset.
Altera Corporation 9–45 January 2005 Stratix GX Transceiver User Guide Recommended Resets
■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Receive Only Datapath : Single Width(8/10 bits) receive parallel clock: rx_coreclk Functional Mode :'Any' RX PLL CRU : rx_cruclk
***************************************************************/
`timescale 1ns/10ps
module reset_seq_rx_rx_cruclk_rx_coreclk ( rx_coreclk, rx_cruclk,
sync_reset, async_reset, receive_digitalreset, rx_freqlocked,
rxanalogreset, rxdigitalreset
);
input rx_cruclk; //Receive GXB input reference clock input rx_coreclk;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode'
9–46 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal
reg rxdigitalreset;
reg rxdigitalreset_rx_cruclk; reg rxdigitalreset_rx_coreclk_Q; reg rxanalogreset;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
//Receive Reset Sequence always @(posedge rx_cruclk or posedge async_reset) if(async_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin if(sync_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk<= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin rxanalogreset <= 1'b0; if (rx_freqlocked) begin if(waitstate_timer == 0) begin waitstate_timer <= waitstate_timer;
if(receive_digitalreset)
rxdigitalreset_rx_cruclk <= 1'b1; else
rxdigitalreset_rx_cruclk <= 1'b0; end else
Altera Corporation 9–47 January 2005 Stratix GX Transceiver User Guide Recommended Resets
begin waitstate_timer <= waitstate_timer - 1'b1;
rxdigitalreset_rx_cruclk <= 1'b1; end end else begin
rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end end end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is used for Receive GXB, then this synchronization is needed because internally the rxdigitalreset is only synchronized to recovered clock (rx_clkout). To reset the rx_coreclk domain logic in PLD fabric following reset is useful */
always @(posedge rx_coreclk or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_coreclk_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_coreclk_Q <= rxdigitalreset_rx_cruclk; rxdigitalreset <= rxdigitalreset_rx_coreclk_Q; end end
endmodule
9–48 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Design Example 2 This design example shows a receive-only configuration with rx_cruclk as the receive CRU input reference clock and rx_clkout as the receive parallel interface clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset. ■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
we have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Receive Only Datapath : Single Width(8/10 bits) or Double Width(16/20 bits) receive parallel clock: rx_clkout Functional Mode :'Any' RX PLL CRU : rx_cruclk
***************************************************************/
Altera Corporation 9–49 January 2005 Stratix GX Transceiver User Guide Recommended Resets
`timescale 1ns/10ps
module reset_seq_rx_rx_cruclk_rx_clkout ( rx_clkout, rx_cruclk,
sync_reset, async_reset, receive_digitalreset, rx_freqlocked,
rxanalogreset, rxdigitalreset
);
input rx_cruclk; //Receive GXB input reference clock input rx_clkout;//Receive recovered clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input receive_digitalreset; //Input : Reset the receiver section
input rx_freqlocked; //rx_freqlocked signal from receive; Transition from 'lock to reference clock mode' to 'lock to data mode'
output rxdigitalreset;//GXB Receive digital reset output rxanalogreset;//Receive power down signal
reg rxdigitalreset;
reg rxdigitalreset_rx_cruclk; reg rxdigitalreset_rx_clkout_Q; reg rxanalogreset;
//Parameter value of T (2ms)based on the fastest clock (or 3.1875 Gbps) parameter WAITSTATE_TIMER_VALUE = 1000000;
reg [19:0]waitstate_timer; //timer - for actual value, refer stratix data sheet
//Receive Reset Sequence always @(posedge rx_cruclk or posedge async_reset) if(async_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE;
9–50 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
end else begin if(sync_reset) begin rxanalogreset <= 1'b1; rxdigitalreset_rx_cruclk<= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end else begin rxanalogreset <= 1'b0; if (rx_freqlocked) begin if(waitstate_timer == 0) begin waitstate_timer <= waitstate_timer;
if(receive_digitalreset)
rxdigitalreset_rx_cruclk <= 1'b1; else
rxdigitalreset_rx_cruclk <= 1'b0; end else begin waitstate_timer <= waitstate_timer - 1'b1;
rxdigitalreset_rx_cruclk <= 1'b1; end end else begin
rxdigitalreset_rx_cruclk <= 1'b1; waitstate_timer <= WAITSTATE_TIMER_VALUE; end end end
/*synchronizing the rxdigitalreset to recovered clock domain If rxdigitalreset is only used for Receive GXB, then this synchronization is not needed because internally the rxdigitalreset is only synchronized to recovered clock (rx_clkout). In the above description of the module, a designer likes to operate on the system clock or PLD clock domain where one would like to have a FIFO with rx_clkout domain being write clock and may have pld clock domain(Generic name, can be any clock name) as read clock. pld clock is optional. To reset the rx_clkout domain logic in PLD fabric following reset is useful*/
Altera Corporation 9–51 January 2005 Stratix GX Transceiver User Guide Recommended Resets
always @(posedge rx_clkout or posedge async_reset) if(async_reset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1;
end else begin if(receive_digitalreset) begin rxdigitalreset_rx_clkout_Q <= 1'b1; rxdigitalreset <= 1'b1; end else begin rxdigitalreset_rx_clkout_Q <= rxdigitalreset_rx_cruclk; rxdigitalreset <= rxdigitalreset_rx_clkout_Q; end end
endmodule
Transmitter Reset
The configurations and design examples in this section show how to implement a reset sequence for the transmitter channels. In this configuration, GXB is configured only as a transmitter. In the design examples, the tx_coreclk option is not shown because the reset signals (txdigitalreset) based on tx_coreclk are synchronized internally by the reset controller in the Stratix GX hard IP. This configuration only demonstrates the reset sequence. You might want to add additional escape states and other system-specific features in your design. If your design requirements are different from the design example, you can make necessary changes, using the flow chart and waveform figures in each section as guidelines.
9–52 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
Figure 9–14. Transmitter Only Clock Options
Transmit ONLY
data path width
Single Width Double Width (8/10) (16/20)
Transmit Parallel Clock
tx_coreclk inclk tx_coreclk inclk
Figure 9–15 shows a situation where only the transmitter channel requires a reset sequence.
Figure 9–15. Transmitter Reset Sequence
Start
async_reset or sync_reset
pll_areset = high txdigitalreset = high
pll_areset = low txdigitalreset = high
NO pll_locked = high pll_areset = low txdigitalreset = high
YES
YES
pll_areset = low transmit_digitalreset = high txdigitalreset = low NO
Altera Corporation 9–53 January 2005 Stratix GX Transceiver User Guide Recommended Resets
The waveform in Figure 9–16 shows the functionality of the transmitter reset sequence shown in Figure 9–15. As described in Table 9–1 on page 9–3, the pll_areset resets the entire transceiver block, including both the analog and digital portions of the transmitter and receiver. After this signal is deasserted, the controller waits until the transmitter PLL is stable (pll_locked = 1'b1) before deasserting tx_digitalreset. This ensures that the output of the transmitter PLL is stable before releasing any of the logic that it feeds.
Figure 9–16. Transmitter Reset Sequence Waveform
Reset Signals 12
pll_areset
4 tx_digitalreset
Stable TXPLL Clock Output Status 3
pll_locked
Design Example 1 This design example shows a transmit-only configuration with inclk as both the transmit PLL input reference clock and the transmit parallel interface clock.
This design example has the following constraints:
■ If your design requirements are different from the examples, use the flow charts and waveforms for each configuration as design guidelines. ■ The design example requires a reset controller that generates a sync_reset (synchronous reset) for the entire system. ■ The design example has an async_reset (a power down in GXB terms) and digital resets for transmit and receive. All user input digital resets must be at least four cycles long. ■ This design example does not cover all the digital reset scenarios in a system that resets the digital logic of the GXB. ■ In this example, whenever the rx_freqlocked signal toggles the rxdigitalreset, the receiver’s digital circuit is reset. However, you can make changes to the design to avoid this if, for example, you want to debug your design without the core being reset.
9–54 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
■ If you plan to use REFCLKB pins in your design, see Appendix C, REFCLKB Pin Constraints for information about the effects of analog resets (pll_arest, rx_analogreset).
/* Copyright (c) Altera Corporation, 2004. This file may contain proprietary and confidential information of Altera Corporation
Contacting Altera ======
We have made every effort to ensure that this design example works correctly. If you have a question that is not answered by the information, please contact Altera Support.
**************************************************************** Reset Sequence for the ALTGXB. The configuration of GXB for which the following reset sequence is valid is: Transmit and Receive : Transmit ONLY Datapath : Single Width(8/10 bits) or Double Width (16/20 bits) Transmit parallel clock: '-' Functional Mode :'Any'
***************************************************************/
`timescale 1ns/10ps
module reset_seq_tx_ONLY (
inclk,
sync_reset, async_reset, transmit_digitalreset, pll_locked,
pll_areset, txdigitalreset
);
input inclk; //GXB input reference clock
input sync_reset; //Input: synchronous reset from the system input async_reset; //Input: async reset from system input transmit_digitalreset; //Input: Reset only the transmit digital section
input pll_locked; // Transmit PLL of GXB locked
Altera Corporation 9–55 January 2005 Stratix GX Transceiver User Guide Recommended Resets
output txdigitalreset; //GXB transmit digital reset output pll_areset;//GXB power down signal
reg txdigitalreset; reg pll_areset; reg [1:0] state;
parameter IDLE = 2'b00; parameter STROBE_TXPLL_LOCKED = 2'b01;
always @ (posedge inclk or posedge async_reset) begin if (async_reset) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end else case (state) IDLE: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED;
end else begin
pll_areset <= 1'b0; state <= IDLE; if(transmit_digitalreset) txdigitalreset <= 1'b1; else txdigitalreset <= 1'b0; end
STROBE_TXPLL_LOCKED: if (sync_reset) //Synchronous Reset can be asserted in IDLE state (After reset seq has finished) begin
txdigitalreset <= 1'b1; pll_areset <= 1'b1; state <= STROBE_TXPLL_LOCKED; end //Wait untill the TXPLL is locked to inclk and TX PLL has a stable output clock which is also fed to RX CRU
9–56 Altera Corporation Stratix GX Transceiver User Guide January 2005 Reset Control & Power Down
else if (pll_locked) begin state <= IDLE; txdigitalreset <= 1'b0; pll_areset <= 1'b0; end else begin state <= STROBE_TXPLL_LOCKED; txdigitalreset <= 1'b1; pll_areset <= 1'b0; end
default: state = IDLE; endcase end
endmodule
Power Down The Quartus II software automatically selects the power-down feature when you configure the Stratix GX device. All unused transceiver channels and transceiver blocks in a design are powered down to reduce the overall power consumption. The power-down feature cannot be used on the fly to turn the transceiver channels/transceiver blocks on/off without reconfiguration.
Table 9–2 details the state of the transceiver I/O pins during power- down.
Table 9–2. I/O Pin States During Power-Down (Part 1 of 2)
Operation Transmitter Pins Receiver Pins REFCLKB Pins Rref Pin Normal operation Transmitter Receiver Clk input Ext. reference R Power down Tri-state (1) Tri-state (1) Tr i-sta te (2) Low (3)
Altera Corporation 9–57 January 2005 Stratix GX Transceiver User Guide Power Down
Table 9–2. I/O Pin States During Power-Down (Part 2 of 2)
Operation Transmitter Pins Receiver Pins REFCLKB Pins Rref Pin PMA loop Serial loop Tr i-state (4) Low (5) —— back back toggle Reverse Transmitter (6) Receiver — — serial loop back
Notes to Table 9–2: (1) Either leave these pins floating or connect n_leg to GXB_GND through a 10-kΩ resistor and connect p_leg to GXB_VCC through a 10-kΩ resistor to improve the device’s immunity to noise. (2) Either leave these pins floating or connect refclkb(+) to GXB_GND through a 10-kΩ resistor and connect refclkb(-) to GXB_VCC through a 10-kΩ resistor to improve the device’s immunity to noise. (3) Altera recommends driving the reference resistor pin low for the powered down transceiver block. (4) Transmitter output is tri-stated at the lowest VOD setting and is toggling at any other setting. However, the VOD is 80% of the selected VOD setting. (5) Receiver pin is pulled low internally. It must be either left floating or pulled low externally. (6) Only the 4-mA setting is supported for reverse serial loopback.
9–58 Altera Corporation Stratix GX Transceiver User Guide January 2005 Appendix A. Data & Control Codes
8B/10B Code This appendix provides information about the data and control codes for the Stratix® GX device.
Code Notation
The 8B/10B data and control codes are referred to as Dx.y and Kx.y, respectively. The 8-bit byte (H G F E D C B A, where H is the MSB and A is the LSB) is broken up into 2 groups, x and y, where x is the 5 lower bits (E D C B A) and y is the upper 3 bits (H G F). Figure A–1 shows the notation for 3C hexadecimal.
Figure A–1. Sample Notation for 3C Hexadecimal
y = 1 x=28
D28.1 0 0 1 1 1 1 0 0 = (3C hex) HGF EDCBA
There are 256 Dx.y and 12 Kx.y valid 8-bit codes. These codes have two 10-bit equivalent codes associated with each 8-bit code. The 10-bit codes can have either a neutral disparity or a non-neutral disparity. In the case of a neutral disparity, 2 neutral disparity 10-bit codes are associated with an 8-bit code. In the case of a non-neutral disparity 10-bit code, a positive and a negative disparity code are associated with the 8-bit code.
The positive disparity 10-bit code is associated with the RD- column, and the negative disparity 10-bit code is associated with the RD+ column.
Disparity Calculation
The running disparity is calculated based on the sub-blocks of the 10-bit code. The 10-bit code is divided into 2 sub blocks, a 6-bit sub-block (abcdei) and a 4-bit sub-block (fghj), as shown in Figure A–2.
Altera Corporation A–1 January 2005 8B/10B Code
Figure A–2. 10-Bit Grouping of 6-Bit & 4-Bit Sub-Blocks
10-Bit Code
jhgf iedcba
9 8 7 6 5 4 3 2 1 0
4-Bit Block 6-Bit Block
The running disparity at the beginning of the 6-bit sub-block is the running disparity at the end of the previous 10-bit code. The running disparity of the 4-bit sub-block is the running disparity of the end of the 6-bit sub-block. The running disparity of the end of the 4-bit sub-block is the running disparity of the 10-bit code, as shown in Figure A–3.
Figure A–3. Running Disparity Between Sub-Blocks
10-Bit Code 10-Bit Code
RD- 0 1 0 0 RD+ 0 1 1 1 0 0 RD+ 1 1 0 0 RD+ 1 1 0 1 0 1
4-Bit Block 6-Bit Block 4-Bit Block 6-Bit Block Last Bit 1st Bit Received Received
The running disparity calculation rules are as follows (if the conditions are not met, then the running disparity at the end of the sub-blocks are the same as the beginning of the sub-block):
■ The current running disparity at the end of a sub-block is positive if any of the following are true:
● The sub-block contains more ones than zeros. ● The 6-bit sub-block is 6'b000111. ● The 4-bit sub-block is 4'b0011.
■ The current running disparity at the end of a sub-block is negative if any of the following are true:
● The sub-block contains more zeros than ones. ● The 6-bit sub-block is 6'b111000. ● The 4-bit sub-block is 4'b1100.
A–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Supported Codes
The 8B/10B scheme defines the 12 control codes listed in Table A–1 for synchronization, alignment, and general application purposes.
Table A–1. Supported K Codes
8-Bit Code 10-Bit Code RD- 10-Bit Code RD+ K Code Octal Value HGF_EDCBA abcdei_fghj abcdei_fghj K28.0 1C 8'b000_11100 10'b001111_0100 10'b110000_1011 K28.1 3C 8'b001_11100 10'b001111_1001 10'b110000_0110 K28.2 5C 8'b010_11100 10'b001111_0101 10'b110000_1010 K28.3 7C 8'b011_11100 10'b001111_0011 10'b110000_1100 K28.4 9C 8'b100_11100 10'b001111_0010 10'b110000_1101 K28.5 (1) BC 8'b101_11100 10'b001111_1010 10'b110000_0101 K28.6 DC 8'b110_11100 10'b001111_0110 10'b110000_1001 K28.7 FC 8'b111_11100 10'b001111_1000 10'b110000_0111 K23.7 F7 8'b111_10111 10'b111010_1000 10'b000101_0111 K27.7 FB 8'b111_11011 10'b110110_1000 10'b001001_0111 K29.7 FD 8'b111_11101 10'b101110_1000 10'b010001_0111 K30.7 FE 8'b111_11110 10'b011110_1000 10'b100001_0111
Note to Table A–1: (1) K28.5 is a comma code used for word alignment and indicates an IDLE state.
Table A–2 shows the valid data code-groups.
Table A–2. Valid Data Code-Groups (Part 1 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D0.0 00 000 00000 100111 0100 011000 1011 D1.0 01 000 00001 011101 0100 100010 1011 D2.0 02 000 00010 101101 0100 010010 1011 D3.0 03 000 00011 110001 1011 110001 0100 D4.0 04 000 00100 110101 0100 001010 1011 D5.0 05 000 00101 101001 1011 101001 0100 D6.0 06 000 00110 011001 1011 011001 0100 D7.0 07 000 00111 111000 1011 000111 0100 D8.0 08 000 01000 111001 0100 000110 1011
Altera Corporation A–3 January 2005 Stratix GX Transceiver User Guide 8B/10B Code
Table A–2. Valid Data Code-Groups (Part 2 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D9.0 09 000 01001 100101 1011 100101 0100 D10.0 0A 000 01010 010101 1011 010101 0100 D11.0 0B 000 01011 110100 1011 110100 0100 D12.0 0C 000 01100 001101 1011 001101 0100 D13.0 0D 000 01101 101100 1011 101100 0100 D14.0 0E 000 01110 011100 1011 011100 0100 D15.0 0F 000 01111 010111 0100 101000 1011 D16.0 10 000 10000 011011 0100 100100 1011 D17.0 11 000 10001 100011 1011 100011 0100 D18.0 12 000 10010 010011 1011 010011 0100 D19.0 13 000 10011 110010 1011 110010 0100 D20.0 14 000 10100 001011 1011 001011 0100 D21.0 15 000 10101 101010 1011 101010 0100 D22.0 16 000 10110 011010 1011 011010 0100 D23.0 17 000 10111 111010 0100 000101 1011 D24.0 18 000 11000 110011 0100 001100 1011 D25.0 19 000 11001 100110 1011 100110 0100 D26.0 1A 000 11010 010110 1011 010110 0100 D27.0 1B 000 11011 110110 0100 001001 1011 D28.0 1C 000 11100 001110 1011 001110 0100 D29.0 1D 000 11101 101110 0100 010001 1011 D30.0 1E 000 11110 011110 0100 100001 1011 D31.0 1F 000 11111 101011 0100 010100 1011 D0.1 20 001 00000 100111 1001 011000 1001 D1.1 21 001 00001 011101 1001 100010 1001 D2.1 22 001 00010 101101 1001 010010 1001 D3.1 23 001 00011 110001 1001 110001 1001 D4.1 24 001 00100 110101 1001 001010 1001 D5.1 25 001 00101 101001 1001 101001 1001 D6.1 26 001 00110 011001 1001 011001 1001 D7.1 27 001 00111 111000 1001 000111 1001 D8.1 28 001 01000 111001 1001 000110 1001 D9.1 29 001 01001 100101 1001 100101 1001
A–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table A–2. Valid Data Code-Groups (Part 3 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D10.1 2A 001 01010 010101 1001 010101 1001 D11.1 2B 001 01011 110100 1001 110100 1001 D12.1 2C 001 01100 001101 1001 001101 1001 D13.1 2D 001 01101 101100 1001 101100 1001 D14.1 2E 001 01110 011100 1001 011100 1001 D15.1 2F 001 01111 010111 1001 101000 1001 D16.1 30 001 10000 011011 1001 100100 1001 D17.1 31 001 10001 100011 1001 100011 1001 D18.1 32 001 10010 010011 1001 010011 1001 D19.1 33 001 10011 110010 1001 110010 1001 D20.1 34 001 10100 001011 1001 001011 1001 D21.1 35 001 10101 101010 1001 101010 1001 D22.1 36 001 10110 011010 1001 011010 1001 D23.1 37 001 10111 111010 1001 000101 1001 D24.1 38 001 11000 110011 1001 001100 1001 D25.1 39 001 11001 100110 1001 100110 1001 D26.1 3A 001 11010 010110 1001 010110 1001 D27.1 3B 001 11011 110110 1001 001001 1001 D28.1 3C 001 11100 001110 1001 001110 1001 D29.1 3D 001 11101 101110 1001 010001 1001 D30.1 3E 001 11110 011110 1001 100001 1001 D31.1 3F 001 11111 101011 1001 010100 1001 D0.2 40 010 00000 100111 0101 011000 0101 D1.2 41 010 00001 011101 0101 100010 0101 D2.2 42 010 00010 101101 0101 010010 0101 D3.2 43 010 00011 110001 0101 110001 0101 D4.2 44 010 00100 110101 0101 001010 0101 D5.2 45 010 00101 101001 0101 101001 0101 D6.2 46 010 00110 011001 0101 011001 0101 D7.2 47 010 00111 111000 0101 000111 0101 D8.2 48 010 01000 111001 0101 000110 0101 D9.2 49 010 01001 100101 0101 100101 0101 D10.2 4A 010 01010 010101 0101 010101 0101
Altera Corporation A–5 January 2005 Stratix GX Transceiver User Guide 8B/10B Code
Table A–2. Valid Data Code-Groups (Part 4 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D11.2 4B 010 01011 110100 0101 110100 0101 D12.2 4C 010 01100 001101 0101 001101 0101 D13.2 4D 010 01101 101100 0101 101100 0101 D14.2 4E 010 01110 011100 0101 011100 0101 D15.2 4F 010 01111 010111 0101 101000 0101 D16.2 50 010 10000 011011 0101 100100 0101 D17.2 51 010 10001 100011 0101 100011 0101 D18.2 52 010 10010 010011 0101 010011 0101 D19.2 53 010 10011 110010 0101 110010 0101 D20.2 54 010 10100 001011 0101 001011 0101 D21.2 55 010 10101 101010 0101 101010 0101 D22.2 56 010 10110 011010 0101 011010 0101 D23.2 57 010 10111 111010 0101 000101 0101 D24.2 58 010 11000 110011 0101 001100 0101 D25.2 59 010 11001 100110 0101 100110 0101 D26.2 5A 010 11010 010110 0101 010110 0101 D27.2 5B 010 11011 110110 0101 001001 0101 D28.2 5C 010 11100 001110 0101 001110 0101 D29.2 5D 010 11101 101110 0101 010001 0101 D30.2 5E 010 11110 011110 0101 100001 0101 D31.2 5F 010 11111 101011 0101 010100 0101 D0.3 60 011 00000 100111 0011 011000 1100 D1.3 61 011 00001 011101 0011 100010 1100 D2.3 62 011 00010 101101 0011 010010 1100 D3.3 63 011 00011 110001 1100 110001 0011 D4.3 64 011 00100 110101 0011 001010 1100 D5.3 65 011 00101 101001 1100 101001 0011 D6.3 66 011 00110 011001 1100 011001 0011 D7.3 67 011 00111 111000 1100 000111 0011 D8.3 68 011 01000 111001 0011 000110 1100 D9.3 69 011 01001 100101 1100 100101 0011 D10.3 6A 011 01010 010101 1100 010101 0011 D11.3 6B 011 01011 110100 1100 110100 0011
A–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table A–2. Valid Data Code-Groups (Part 5 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D12.3 6C 011 01100 001101 1100 001101 0011 D13.3 6D 011 01101 101100 1100 101100 0011 D14.3 6E 011 01110 011100 1100 011100 0011 D15.3 6F 011 01111 010111 0011 101000 1100 D16.3 70 011 10000 011011 0011 100100 1100 D17.3 71 011 10001 100011 1100 100011 0011 D18.3 72 011 10010 010011 1100 010011 0011 D19.3 73 011 10011 110010 1100 110010 0011 D20.3 74 011 10100 001011 1100 001011 0011 D21.3 75 011 10101 101010 1100 101010 0011 D22.3 76 011 10110 011010 1100 011010 0011 D23.3 77 011 10111 111010 0011 000101 1100 D24.3 78 011 11000 110011 0011 001100 1100 D25.3 79 011 11001 100110 1100 100110 0011 D26.3 7A 011 11010 010110 1100 010110 0011 D27.3 7B 011 11011 110110 0011 001001 1100 D28.3 7C 011 11100 001110 1100 001110 0011 D29.3 7D 011 11101 101110 0011 010001 1100 D30.3 7E 011 11110 011110 0011 100001 1100 D31.3 7F 011 11111 101011 0011 010100 1100 D0.4 80 100 00000 100111 0010 011000 1101 D1.4 81 100 00001 011101 0010 100010 1101 D2.4 82 100 00010 101101 0010 010010 1101 D3.4 83 100 00011 110001 1101 110001 0010 D4.4 84 100 00100 110101 0010 001010 1101 D5.4 85 100 00101 101001 1101 101001 0010 D6.4 86 100 00110 011001 1101 011001 0010 D7.4 87 100 00111 111000 1101 000111 0010 D8.4 88 100 01000 111001 0010 000110 1101 D9.4 89 100 01001 100101 1101 100101 0010 D10.4 8A 100 01010 010101 1101 010101 0010 D11.4 8B 100 01011 110100 1101 110100 0010 D12.4 8C 100 01100 001101 1101 001101 0010
Altera Corporation A–7 January 2005 Stratix GX Transceiver User Guide 8B/10B Code
Table A–2. Valid Data Code-Groups (Part 6 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D13.4 8D 100 01101 101100 1101 101100 0010 D14.4 8E 100 01110 011100 1101 011100 0010 D15.4 8F 100 01111 010111 0010 101000 1101 D16.4 90 100 10000 011011 0010 100100 1101 D17.4 91 100 10001 100011 1101 100011 0010 D18.4 92 100 10010 010011 1101 010011 0010 D19.4 93 100 10011 110010 1101 110010 0010 D20.4 94 100 10100 001011 1101 001011 0010 D21.4 95 100 10101 101010 1101 101010 0010 D22.4 96 100 10110 011010 1101 011010 0010 D23.4 97 100 10111 111010 0010 000101 1101 D24.4 98 100 11000 110011 0010 001100 1101 D25.4 99 100 11001 100110 1101 100110 0010 D26.4 9A 100 11010 010110 1101 010110 0010 D27.4 9B 100 11011 110110 0010 001001 1101 D28.4 9C 100 11100 001110 1101 001110 0010 D29.4 9D 100 11101 101110 0010 010001 1101 D30.4 9E 100 11110 011110 0010 100001 1101 D31.4 9F 100 11111 101011 0010 010100 1101 D0.5 A0 101 00000 100111 1010 011000 1010 D1.5 A1 101 00001 011101 1010 100010 1010 D2.5 A2 101 00010 101101 1010 010010 1010 D3.5 A3 101 00011 110001 1010 110001 1010 D4.5 A4 101 00100 110101 1010 001010 1010 D5.5 A5 101 00101 101001 1010 101001 1010 D6.5 A6 101 00110 011001 1010 011001 1010 D7.5 A7 101 00111 111000 1010 000111 1010 D8.5 A8 101 01000 111001 1010 000110 1010 D9.5 A9 101 01001 100101 1010 100101 1010 D10.5 AA 101 01010 010101 1010 010101 1010 D11.5 AB 101 01011 110100 1010 110100 1010 D12.5 AC 101 01100 001101 1010 001101 1010 D13.5 AD 101 01101 101100 1010 101100 1010
A–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table A–2. Valid Data Code-Groups (Part 7 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D14.5 AE 101 01110 011100 1010 011100 1010 D15.5 AF 101 01111 010111 1010 101000 1010 D16.5 B0 101 10000 011011 1010 100100 1010 D17.5 B1 101 10001 100011 1010 100011 1010 D18.5 B2 101 10010 010011 1010 010011 1010 D19.5 B3 101 10011 110010 1010 110010 1010 D20.5 B4 101 10100 001011 1010 001011 1010 D21.5 B5 101 10101 101010 1010 101010 1010 D22.5 B6 101 10110 011010 1010 011010 1010 D23.5 B7 101 10111 111010 1010 000101 1010 D24.5 B8 101 11000 110011 1010 001100 1010 D25.5 B9 101 11001 100110 1010 100110 1010 D26.5 BA 101 11010 010110 1010 010110 1010 D27.5 BB 101 11011 110110 1010 001001 1010 D28.5 BC 101 11100 001110 1010 001110 1010 D29.5 BD 101 11101 101110 1010 010001 1010 D30.5 BE 101 11110 011110 1010 100001 1010 D31.5 BF 101 11111 101011 1010 010100 1010 D0.6 C0 110 00000 100111 0110 011000 0110 D1.6 C1 110 00001 011101 0110 100010 0110 D2.6 C2 110 00010 101101 0110 010010 0110 D3.6 C3 110 00011 110001 0110 110001 0110 D4.6 C4 110 00100 110101 0110 001010 0110 D5.6 C5 110 00101 101001 0110 101001 0110 D6.6 C6 110 00110 011001 0110 011001 0110 D7.6 C7 110 00111 111000 0110 000111 0110 D8.6 C8 110 01000 111001 0110 000110 0110 D9.6 C9 110 01001 100101 0110 100101 0110 D10.6 CA 110 01010 010101 0110 010101 0110 D11.6 CB 110 01011 110100 0110 110100 0110 D12.6 CC 110 01100 001101 0110 001101 0110 D13.6 CD 110 01101 101100 0110 101100 0110 D14.6 CE 110 01110 011100 0110 011100 0110
Altera Corporation A–9 January 2005 Stratix GX Transceiver User Guide 8B/10B Code
Table A–2. Valid Data Code-Groups (Part 8 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D15.6 CF 110 01111 010111 0110 101000 0110 D16.6 D0 110 10000 011011 0110 100100 0110 D17.6 D1 110 10001 100011 0110 100011 0110 D18.6 D2 110 10010 010011 0110 010011 0110 D19.6 D3 110 10011 110010 0110 110010 0110 D20.6 D4 110 10100 001011 0110 001011 0110 D21.6 D5 110 10101 101010 0110 101010 0110 D22.6 D6 110 10110 011010 0110 011010 0110 D23.6 D7 110 10111 111010 0110 000101 0110 D24.6 D8 110 11000 110011 0110 001100 0110 D25.6 D9 110 11001 100110 0110 100110 0110 D26.6 DA 110 11010 010110 0110 010110 0110 D27.6 DB 110 11011 110110 0110 001001 0110 D28.6 DC 110 11100 001110 0110 001110 0110 D29.6 DD 110 11101 101110 0110 010001 0110 D30.6 DE 110 11110 011110 0110 100001 0110 D31.6 DF 110 11111 101011 0110 010100 0110 D0.7 E0 111 00000 100111 0001 011000 1110 D1.7 E1 111 00001 011101 0001 100010 1110 D2.7 E2 111 00010 101101 0001 010010 1110 D3.7 E3 111 00011 110001 1110 110001 0001 D4.7 E4 111 00100 110101 0001 001010 1110 D5.7 E5 111 00101 101001 1110 101001 0001 D6.7 E6 111 00110 011001 1110 011001 0001 D7.7 E7 111 00111 111000 1110 000111 0001 D8.7 E8 111 01000 111001 0001 000110 1110 D9.7 E9 111 01001 100101 1110 100101 0001 D10.7 EA 111 01010 010101 1110 010101 0001 D11.7 EB 111 01011 110100 1110 110100 1000 D12.7 EC 111 01100 001101 1110 001101 0001 D13.7 ED 111 01101 101100 1110 101100 1000 D14.7 EE 111 01110 011100 1110 011100 1000 D15.7 EF 111 01111 010111 0001 101000 1110
A–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table A–2. Valid Data Code-Groups (Part 9 of 9)
Octet Bits Current RD- Current RD+ Code-group Name Octet Value HGF EDCBA abcdei fghj abcdei fghj D16.7 F0 111 10000 011011 0001 100100 1110 D17.7 F1 111 10001 100011 0111 100011 0001 D18.7 F2 111 10010 010011 0111 010011 0001 D19.7 F3 111 10011 110010 1110 110010 0001 D20.7 F4 111 10100 001011 0111 001011 0001 D21.7 F5 111 10101 101010 1110 101010 0001 D22.7 F6 111 10110 011010 1110 011010 0001 D23.7 F7 111 10111 111010 0001 000101 1110 D24.7 F8 111 11000 110011 0001 001100 1110 D25.7 F9 111 11001 100110 1110 100110 0001 D26.7 FA 111 11010 010110 1110 010110 0001 D27.7 FB 111 11011 110110 0001 001001 1110 D28.7 FC 111 11100 001110 1110 001110 0001 D29.7 FD 111 11101 101110 0001 010001 1110 D30.7 FE 111 11110 011110 0001 100001 1110 D31.7 FF 111 11111 101011 0001 010100 1110
Altera Corporation A–11 January 2005 Stratix GX Transceiver User Guide 8B/10B Code
A–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 Appendix B. Ports & Parameters
Input Ports Table B–1 lists the input ports of the Stratix® GX device.
Table B–1. Input Ports (Part 1 of 4)
Port Name Required Description Comments inclk[] See Transceiver block Input port [NUMBER_OF_QUADS - 1..0] comments transmitter PLL wide. If you use the transmitter PLL, the reference input inclk[] port is required. If you set the clock. OPERATION_MODE parameter to TX or DUPLEX, the inclk[] port is required. pll_areset[] No Asynchronous reset Input port [NUMBER_OF_QUADS - 1..0] for the transceiver wide. block transmitter PLL. This signal powers down the entire transceiver block. When placing refclkb pins, see Appendix C, REFCLKB Pin Constraints for information about analog reads and refclkb pin usage constraints. rx_in[] Yes Transceiver block Input port [NUMBER_OF_CHANNELS - receiver channel 1..0] wide. data input port. rx_cruclk[] No Clock recovery unit Input port [NUMBER_OF_QUADS - 1..0] (CRU) for the wide. When you set the transceiver block OPERATION_MODE parameter to TX or receiver PLL DUPLEX, the rx_cruclk[] port cannot reference input be used. If you use this parameter, the clock. transceiver block transmitter PLL cannot be instantiated. rx_bitslip[] No Controls bit slipping Input port [NUMBER_OF_CHANNELS - circuitry in the word 1..0] wide. If you enable the rx_bitslip aligner. port, the rx_enacdet[] port cannot be connected and the USE_AUTO_BIT_SLIP parameter must be set to OFF.
Altera Corporation B–1 January 2005 Input Ports
Table B–1. Input Ports (Part 2 of 4)
Port Name Required Description Comments rx_enacdet[] No Enables alignment Input port [NUMBER_OF_CHANNELS - to the programmed 1..0] wide. If you enable the rx_enacdet pattern. port, the rx_bitslip[] port cannot be connected, and the USE_AUTO_BIT_SLIP parameter must be set to ON. rx_slpbk[] No Serial loopback Input port [NUMBER_OF_CHANNELS - input. Dynamically 1..0] wide. If you enable the rx_slpbk[] enables serial input port, the OPERATION_MODE loopback from the parameter must be set to DUPLEX, and the transceiver block serialfdbk port of the transceiver block transmitter to the receiver channel must be connected. transceiver block receiver in the same channel. rx_a1a2size[] No Detects A1A2 or Input port [NUMBER_OF_CHANNELS - A1A1A2A2 input 1..0] wide. If you enable the patterns. If the rx_a1a2size[] port, the PROTOCOL signal is low (0), parameter must be set to SONET. A1A2 patterns are detected. If the signal is high (1), A1A1A2A2 patterns are detected. rx_equalizerctrl[] No Specifies the Input port [NUMBER_OF_CHANNELS * equalizer control 3..0] wide. Use the following settings: setting. Incoming Signal Equalizer Control Setting 000 0 001 Reserved 010 1 011 Reserved 100 2 101 3 110 Reserved 111 4 rx_locktorefclk[] No Control signal for Input port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. receiver PLL to lock to the reference clock.
B–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table B–1. Input Ports (Part 3 of 4)
Port Name Required Description Comments rx_locktodata[] No Control signal for Input port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. The rx_locktodata[] port receiver PLL to lock can overwrite the rx_locktorefclk[] the received data. port. tx_in[] Yes Transceiver block Input port [CHANNEL_WIDTH * transmitter channel NUMBER_OF_CHANNELS - 1..0] wide. If data input port. you set the USE_8B_10B_MODE parameter to OFF and the USE_DOUBLE_DATA_MODE parameter is set to OFF, the deserialization factor is CHANNEL_WIDTH. If you set the USE_8B_10B_MODE parameter to OFF and the USE_DOUBLE_DATA_MODE parameter is set to ON, the deserialization factor is CHANNEL_WIDTH / 2. If you set the USE_8B_10B_MODE parameter to ON, the deserialization factor is 10. tx_ctrlenable[] No Control character Input port [NUMBER_OF_CHANNELS * enable. Enables the DWIDTH_FACTOR - 1..0] wide. If 8B/10B encoder to tx_ctrlenable[] port is high, the sent identify control word is a control character. characters. Labels an input character as a control code. tx_srlpbk[] No Reverse serial Input port [NUMBER_OF_CHANNELS - loopback input. 1..0] wide. Dynamically enables reverse serial loopback from the rx_in[] port to the tx_out[] port
Altera Corporation B–3 January 2005 Stratix GX Transceiver User Guide Input Ports
Table B–1. Input Ports (Part 4 of 4)
Port Name Required Description Comments tx_vodctrl[] No 3-bit control signal Input port [NUMBER_OF_CHANNELS * 3 - that dynamically 1..0] wide. Use the following settings: specifies the Voltage Output Incoming Signal VOD Control Differential (VOD) Setting control settings. 000 400 mV 001 800 mV 010 1,000 mV 011 1,200 mV 100 1,400 mV 101 1,600 mV 110 1,600 mV 111 1,600 mV tx_preemphasisctrl[] No 3-bit control signal Input port [NUMBER_OF_CHANNELS * 3 - that dynamically 1..0] wide. Use the following settings: specifies the pre- Incoming Pre-emphasis emphasis settings. Signal Setting 000 0 001 1 010 2 011 3 100 4 101 5 110 5 111 5 txdigitalreset[] No Sends a reset signal Input port [NUMBER_OF_QUADS * 4 - to the digital portion 1..0] wide. of the transmitter. rxdigitalreset[] No Sends a reset signal Input port [NUMBER_OF_QUADS * 4 - to the digital portion 1..0] wide. of the receiver. rxanalogreset[] No Sends a power Input port [NUMBER_OF_QUADS * 4 - down signal to the 1..0] wide. analog portion of the receiver. pllenable[] No Sends an enable Input port [NUMBER_OF_QUADS - 1..0] signal to the wide. transceiver block transmitter PLL. pll_areset[] No Sends a power Input port [NUMBER_OF_QUADS - 1..0] down signal to the wide. transceiver block transmitter PLL.
B–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 Output Ports Table B–2 lists the output ports of the Stratix GX device.
Table B–2. Output Ports (Part 1 of 4)
Port Name Required Description Comments pll_locked[] No Gives the status of the Output port [NUMBER_OF_QUADS - 1..0] transceiver block wide. The pll_locked port is available transmitter PLL. only when the transceiver block transmitter PLL is used. The signal achieves lock status within several clock cycles in simulation. This does not necessarily reflect the real lock time in the hardware, which can take thousands of cycles for some settings. coreclk_out[] No Output clock fed by the Output port [NUMBER_OF_QUADS - 1..0] clk2 port of the wide. If a transceiver block transmitter PLL transceiver block is used, the coreclk_out port must be transmitter PLL. enabled. rx_out[] Yes Transceiver block Output port [CHANNEL_WIDTH * receiver PLL output NUMBER_OF_CHANNELS - 1..0] wide. If data. you set the USE_8B_10B_MODE parameter to OFF and the USE_DOUBLE_DATA_MODE parameter is set to OFF, the deserialization factor is CHANNEL_WIDTH. If you set the USE_8B_10B_MODE parameter to OFF and the USE_DOUBLE_DATA_MODE parameter is set to ON, the deserialization factor is CHANNEL_WIDTH / 2. If you set the USE_8B_10B_MODE parameter to ON, the deserialization factor is 10.
Altera Corporation B–5 January 2005 Stratix GX Transceiver User Guide Output Ports
Table B–2. Output Ports (Part 2 of 4)
Port Name Required Description Comments rx_clkout[] No Output clock from the Output port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. If you set the receiver channel. USE_RATE_MATCH_FIFO parameter to ON and the CLK_OUT_MODE_REFERENCE parameter is set to ON, the rx_clkout[] port is the PLL reference clock with the period PLL_INCLOCK_PERIOD / DATA_RATE) * CHANNEL_WIDTH. If you set the USE_RATE_MATCH_FIFO parameter to ON and the CLK_OUT_MODE_REFERENCE parameter is set to OFF, the rx_clkout[] port is the clock output of the PLL. If you set the USE_RATE_MATCH_FIFO parameter is OFF, the value of the rx_clkout[] port is the same as the value of the rx_recovclockout[] port. If you set the USE_DOUBLE_DATA_MODE parameter OFF, the clock period must be doubled, or the clock frequency must be halved. rx_locked[] No Gives the status of the Output port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. Indicates that the transceiver receiver channel atom. block receiver PLL is locked to the reference input clock (active low). When the transceiver block receiver PLL is locked, this signal is GND. When the transceiver block receiver PLL is out of lock, this signal is VCC. The signal achieves lock status within several clock cycles in simulation. This does not necessarily reflect the real lock time in hardware, which can take thousands of cycles for some settings. rx_channelaligned[] Yes Channel alignment Output port [NUMBER_OF_QUADS - 1..0] status for the wide. If the PROTOCOL parameter is set to transceiver block XAUI, the rx_channelaligned[] port receiver channels. must be connected.
B–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table B–2. Output Ports (Part 3 of 4)
Port Name Required Description Comments rx_freqlocked[] No Indicates whether Output port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. This port is asserted when the receiver channel is GXB receiver PLL moves to lock to the locked to the data mode received data mode. At that time, the clock in the rx_in[] port. recovery unit (CRU) for the GXB receiver PLL is frequency and phase-locked to the reference clock and starts using the phase detector to lock onto the incoming data, but it is not yet locked to the data. It takes a finite time before the CRU for the GXB receiver PLL is locked onto the data. The signal achieves lock status within several clock cycles in simulation. This does not necessarily reflect the real lock time in hardware, which can take thousands of cycles for some settings. rx_rlv[] No Indicates whether the Output port [NUMBER_OF_CHANNELS - transceiver block 1..0] wide. receiver channel violated the value specified for the RUN_LENGTH parameter. rx_syncstatus[] No Provides the status of Output port [NUMBER_OF_CHANNELS * the pattern detector DWIDTH_FACTOR - 1..0] wide. If you set and word aligner. the PROTOCOL parameter to XAUI or GigE, the rx_syncstatus[] port is connected to the synchronization state machine and indicates that the channel completed synchronization. If you set the PROTOCOL parameter to anything other than XAUI or GigE, the rx_syncstatus[] port becomes a resync signal for manual synchronization of the alignment system. rx_patterndetect[] No Indicates whether the Output port [NUMBER_OF_CHANNELS * pattern detector DWIDTH_FACTOR - 1..0] wide. detected the programmed pattern. rx_ctrldetect[] No Indicates whether the Output port [NUMBER_OF_CHANNELS * 8B/10B decoder DWIDTH_FACTOR - 1..0] wide. If you set detects a control code. the USE_8B_10B_MODE parameter to OFF, the rx_ctrldetect port is not available.
Altera Corporation B–7 January 2005 Stratix GX Transceiver User Guide Output Ports
Table B–2. Output Ports (Part 4 of 4)
Port Name Required Description Comments rx_errdetect[] No Indicates whether the Output port [NUMBER_OF_CHANNELS * 8B/10B decoder DWIDTH_FACTOR - 1..0] wide. If you set detects an error code. the USE_8B_10B_MODE parameter to OFF, the rx_errdetect port is not available. rx_disperr[] No Indicates whether the Output port [NUMBER_OF_CHANNELS * 8B/10B decoder DWIDTH_FACTOR - 1..0] wide. detects a disparity error. rx_signaldetect[] No Indicates whether there Output port [NUMBER_OF_CHANNELS - is a legal voltage level 1..0] wide. This port is available only if the on the input buffer. PROTOCOL parameter is set to XAUI or GigE. This signal is always set in the modes in which it is enabled. It is still enabled even after the signal is a forced HIGH for backward compatibility with existing designs. rx_bisterr[] No Error status signal for Output port [NUMBER_OF_CHANNELS - the self test. 1..0] wide. This port is available only if the USE_SELF_TEST_MODE parameter is turned on. rx_bistdone[] No Indicates whether the Output port [NUMBER_OF_CHANNELS - self test is complete. 1..0] wide. This port is available only if the USE_SELF_TEST_MODE parameter is turned on. rx_a1a2sizeout[] No Reports the Output port [NUMBER_OF_CHANNELS * a1a2size signal as DWIDTH_FACTOR - 1..0] wide. seen by the word aligner. tx_out[] Yes Serialized transceiver Output port [NUMBER_OF_CHANNELS - block transmitter 1..0] wide. channel data signal.
B–8 Altera Corporation Stratix GX Transceiver User Guide January 2005 Parameter Table B–3 describes the Stratix GX device parameters. Descriptions
Table B–3. Parameter Descriptions (Part 1 of 6)
Parameter Type Required Comments OPERATION_MODE String Yes Specifies the operation of the transceiver block transmitter PLL and transceiver block receiver PLL. Values are RX, TX, and DUPLEX. If the PROTOCOL parameter is set to XAUI, then you must set the OPERATION_MODE parameter to DUPLEX. LOOPBACK_MODE String No Specifies the operation of the loopback. Values are NONE, SLB, and PLB. If omitted, the default is NONE. Values other than NONE are available only when the OPERATION_MODE parameter is set to DUPLEX. REVERSE_LOOPBACK String No Specifies the operation of the reverse loopback. _MODE Values are NONE, and RSLB. If omitted, the default is NONE. Values other than NONE are available only when the OPERATION_MODE parameter is set to DUPLEX. PROTOCOL String Yes Specifies the protocol. Values are XAUI, SONET, GigE, and Basic. NUMBER_OF_CHANNELS Integer Yes Specifies the number of transceiver block receiver or transmitter channels. Values are 1 through 20. NUMBER_OF_QUADS Integer Yes Specifies the number of transceiver blocks. CHANNEL_WIDTH Integer Yes Specifies the width of the dataout signal from the transceiver block receiver or transmitter channel atom. Use the following settings: Setting of Channel Width PROTOCOL Values Parameter
XAUI 16 SONET 8 and 16 GigE 8 Basic 8, 10, 16, and 20
For more information, see the table in the comments for the DATA_RATE parameter.
Altera Corporation B–9 January 2005 Stratix GX Transceiver User Guide Parameter Descriptions
Table B–3. Parameter Descriptions (Part 2 of 6)
Parameter Type Required Comments PLL_INCLOCK_PERIOD Integer Yes Specifies, in picoseconds (ps), the period or frequency of the transceiver block transmitter PLL. If omitted, the default is 0. The value of this parameter is used to compute the input clock frequency in MHz; (1 / PLL_INCLOCK_PERIOD) * 1,000,000. When you specify PLL_INCLOCK_PERIOD, the CRU_INCLOCK_PERIOD parameter cannot be used. For more information, see the table in the comments for the DATA_RATE parameter. DATA_RATE Integer Yes Specifies, in Mbps, the rate of data from the transceiver block transmitter channel and the transceiver block receiver channel. If omitted, the default is 0. DATA_RATE_REMAINDER Integer No Specifies, in bits per second (bps), the remainder of the DATA_RATE parameter; DATA_RATE * 1,000,000. This parameter helps to specify non-integral data rates. If omitted, the default is 0. USE_DOUBLE_DATA_MODE String No Specifies whether to use double data width mode. If you enable this parameter, the CHANNEL_WIDTH parameter value is 16 or 20. When the CHANNEL_WIDTH parameter value is 8 or 10, the transceiver block receiver channel is not in double data width mode. Values are ON and OFF. If omitted, the default is OFF. USE_8B_10B_MODE String No Specifies whether to use the 8B/10B decoder. If this parameter is turned on, the deserialization factor is 10, and the CHANNEL_WIDTH parameter value is 8 or 16. Values are ON and OFF. If omitted, the default is OFF. DWIDTH_FACTOR Integer No Specifies the width of the double data factor. Values are 1 and 2. If omitted, the default is 1. A value of 1 means that value of the USE_DOUBLE_DATA_MODE parameter is OFF, and a value of 2 means that value of the USE_DOUBLE_DATA_MODE parameter is ON. CRU_INCLOCK_PERIOD Integer No Specifies, in picoseconds (ps), the period or frequency of the transceiver block receiver PLL. If omitted, the default is 0. The value of this parameter computes the input clock frequency in MHz; (1 / CRU_INCLOCK_PERIOD) * 1,000,000. When you specify the CRU_INCLOCK_PERIOD, the PLL_INCLOCK_PERIOD parameter cannot be used. For more information, see the table in the comments for the DATA_RATE parameter.
B–10 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table B–3. Parameter Descriptions (Part 3 of 6)
Parameter Type Required Comments RUN_LENGTH Integer No Specifies the maximum run length supported for the incoming data signal. This parameter is ignored if the RUN_LENGTH_ENABLE parameter is turned off. If the deserialization factor is 8, legal values are 4–128, in multiples of four. If the deserialization factor is 10, legal values are 5–160, in multiples of five. If omitted, the default is 0. RUN_LENGTH_ENABLE String No Specifies whether to use run length detection. Values are ON and OFF. If omitted, the default is OFF. USE_CHANNEL_ALIGN String No Specifies whether to use the channel aligner and enable the deskew system. The USE_CHANNEL_ALIGN parameter can only be used when the PROTOCOL parameter is set to XAUI. Values are ON and OFF. If omitted, the default is OFF. USE_AUTO_BIT_SLIP String No Specifies whether to use internal bit slipping circuitry. If you enable this parameter, the bitslip transceiver block receiver channel is ignored, and an internal register controls the byte alignment functions. If this parameter is turned off, the bit slipping operation is controlled by the rx_bitslip[] signal. Values are ON and OFF. If omitted, the default is OFF. USE_SYMBOL_ALIGN String No Specifies whether to use the word aligner. Values are ON and OFF. If omitted, the default is ON. ALIGN_PATTERN String No Specifies the pattern of 7, 10, or 16 bits used by the word aligner for the USE_SYMBOL_ALIGN parameter. If the USE_SYMBOL_ALIGN parameter is turned off, this parameter is ignored. If the PROTOCOL parameter is set to XAUI or GigE, the only legal pattern is 0101111100. ALIGN_PATTERN_LENGTH Integer No Specifies the length of the ALIGN_PATTERN parameter. Values are 7, 10, or 16. If omitted, the default is 0. CLK_OUT_MODE_ String No Specifies whether to use the clock that operates the REFERENCE post rate matching FIFO module of the transceiver block receiver channel. This parameter is ignored if the USE_RATE_MATCH_FIFO parameter is turned off. Values are ON and OFF. If omitted, the default is OFF. USE_SELF_TEST_MODE String No Indicates whether to use the built-in self test mode. Values are ON and OFF. If omitted, the default is OFF.
Altera Corporation B–11 January 2005 Stratix GX Transceiver User Guide Parameter Descriptions
Table B–3. Parameter Descriptions (Part 4 of 6)
Parameter Type Required Comments SELF_TEST_MODE Integer No Indicates which self test mode to use. Values are 0, 1, 2, 3, or 4. If omitted, the default is 0. This parameter is ignored if the USE_SELF_TEST_MODE parameter is turned off. Use the following settings: Value Test
0 PRBS 1 00-FF, followed by 5 K28.5+ and repeat 2 High frequency pattern, repeat of D21.5- D21.5+ 3 Low frequency pattern, repeat of K28.7- K28.7+ 4 Mixed frequency pattern, repeat of K28.5- K28.5+
USE_EQUALIZER_ String No Specifies whether to use the equalizer control signal. CTRL_SIGNAL Values are ON and OFF. If omitted, the default is OFF. EQUALIZER_CTRL_ Integer No Specifies the magnitude of the equalizer control SETTING settings. Refer to the Quartus® II help menu for more information regarding the variable values. This parameter should be specified if the USE_EQUALIZER_CTRL_SIGNAL parameter is turned off. SIGNAL_LOSS_ Integer No Specifies the signal loss threshold. Refer to the THRESHOLD_SELECT Quartus II software Help menu for more information about the variable values. PLL_BANDWIDTH_TYPE String No Specifies the transceiver block receiver PLL or the transceiver block transmitter bandwidth type. Values are LOW and HIGH. If omitted, the default is HIGH. RX_BANDWIDTH_TYPE String No Specifies the transceiver block receiver PLL bandwidth type. Values are LOW and HIGH. If omitted, the default is HIGH. PLL_ENABLE_DC_ String No Specifies whether to enable DC coupling on the COUPLING transceiver block transmitter PLL clock input. Values are ON and OFF. If omitted, the default is OFF. RX_ENABLE_DC_ String No Specifies whether to enable DC coupling on the COUPLING transceiver block receiver PLL data input. Values are ON and OFF. If omitted, the default is OFF. USE_VOD_CTRL_SIGNAL String No Specifies whether the VOD control signal is used. If this parameter is turned on, the tx_vodctrl port is used and the VOD_CTRL_SETTING parameter is ignored. Values are ON and OFF. If omitted, the default is OFF.
B–12 Altera Corporation Stratix GX Transceiver User Guide January 2005 Table B–3. Parameter Descriptions (Part 5 of 6)
Parameter Type Required Comments
VOD_CTRL_SETTING Integer No Specifies, in mV, the value of the VOD control signal. Values are 400, 800, 1000, 1200, 1400, 1600. If omitted, the default is 1000. USE_PREEMPHASIS_ String No Specifies whether the pre-emphasis control signal is CTRL_SIGNAL used. If you enable this parameter, the tx_preemphasisctrl port is used and the PREEMPHASIS_CTRL_SETTING parameter is ignored. Values are ON and OFF. If omitted, the default is OFF.
PREEMPHASIS_CTRL_ Integer No Specifies, as a percentage of the VOD control setting, SETTING the value of the pre-emphasis control signal. Values are 0, 1, 2, 3, 4, or 5. If omitted, the default is 0. USE_RX_CLKOUT String No Specifies whether the output clock from the transceiver block receiver channel is used. Values are ON and OFF. If omitted, the default is OFF. If you enable this parameter, the rx_clkout port must be used. USE_RX_CRUCLK String No Specifies whether the clock recovery unit (CRU) is used for the transceiver block receiver PLL reference input clock. Values are ON and OFF. If omitted, the default is OFF. If you enable this parameter, the rx_cruclk port must be used. RX_PPM_SETTING Integer No Specifies the value of the PPM threshold between the transceiver block receiver PLL VCO and the clock recovery unit (CRU). Values are 125, 250, 500, or 1000. If omitted, the default is 1000. RX_FORCE_SIGNAL_ String No Specifies whether the rx_signaldetect[] port is DETECT used. Values are ON and OFF. If omitted, the default is ON. USE_RX_CORECLK String No Specifies whether the rx_coreclk[] port is used. Values are ON and OFF. If omitted, the default is OFF. USE_TX_CORECLK String No Specifies whether the tx_coreclk[] port is used. Values are ON and OFF. If omitted, the default is OFF. FLIP_RX_OUT String No Specifies whether the transceiver block receiver channel output data bits are flipped. Values are ON and OFF. If omitted, the default is OFF. FLIP_TX_IN String No Specifies whether the transceiver block transmitter channel input data bits are flipped. Values are ON and OFF. If omitted, the default is OFF. INSTANTIATE_ String No Specifies whether the transceiver block transmitter TRANSMITTER_PLL PLL is instantiated. Values are ON and OFF. If omitted, the default is OFF.
Altera Corporation B–13 January 2005 Stratix GX Transceiver User Guide Parameter Descriptions
Table B–3. Parameter Descriptions (Part 6 of 6)
Parameter Type Required Comments CONSIDER_INSTANTIATE String No Specifies whether the _TRANSMITTER_PLL INSTANTIATE_TRANSMITTER_PLL parameter is turned on. Values are ON and OFF. If omitted, the default is OFF. TX_TERMINATION Integer No Specifies the termination setting on the pin fed by the transceiver block transmitter channel tx_out[] port. Values are 0, 1, 2, or 3. If omitted, the default is 2. Use the following settings:
Value Termination Setting
0 150 Ω 1 120 Ω 2 100 Ω 3 External termination
RX_DATA_RATE Integer No Specifies, in Mbps, the rate of data from the GXB receiver channel. If omitted, the default is 0. RX_DATA_RATE_REMAINDER Integer No Specifies, in bits per second (bps), the remainder of the RX_DATA_RATE parameter; RX_DATA_RATE * 1000000. This parameter helps to specify non-integral data rates. If omitted, the default is 0. INTENDED_DEVICE_FAMILY String No Use this parameter for modeling and behavioral simulation purposes. Create the altgxb megafunction with the MegaWizard® Plug-in Manager to calculate the value for this parameter.
B–14 Altera Corporation Stratix GX Transceiver User Guide January 2005 Appendix C. REFCLKB Pin Constraints
Known Issues This document discusses issues you might encounter in certain configurations of the Stratix® GX device. These issues are a result of a combination of resource utilization (REFCLKB pins that use Inter Quad (IQ) lines, signals (pllenable, pll_areset, and rxanalogreset), and software modeling.
The potential issues for certain configurations are described below:
1. The pll_areset and pllenable signals in a transceiver block reset its dedicated clock (REFCLKB) pad.
If the design uses the REFCLKB pin of the active transceiver block to feed core logic, there is no clock to the core logic if the pll_areset or pllenable signal is asserted. This problem could be severe if the clock from the REFCLKB pin is also feeding the reset controller/logic in the core logic. The system may never come out of reset in this configuration.
Modeling in the Quartus® II software simulation does not reveal this issue. This issue also exists for multiple transceiver block applications that use the REFCLKB pin for clocking.
2. Asserting the rxanalogreset signal of all four channels in a transceiver block resets its dedicated clock pad.
This might happen if, in the design, only the receive portions of the channels are used and the REFCLKB pin of the transceiver block is used to feed the clock to the core logic. This can affect any logic using the clock from this pad. This behavior is not modeled in the Quartus II software simulation.
If the reference clock to the receiver (rx_cruclk) is routed globally, the clock pad is not in use and will not flat-line the reference clock.
3. When the rxanalogreset signal of all four channels in a transceiver block is asserted, it also resets the transmitter PLL.
Altera Corporation C–1 January 2005 Known Issues
If the design is using the transmitter PLL output to drive any clock into the core (any part of the device), asserting the rxanalogreset signal of all four channels also resets the transmitter PLL and affects the clock that feeds the core logic. This behavior is not modeled in the Quartus II software simulation.
Figure C–1 shows an example of a problem configuration using the Stratix GX 25F device. This configuration is also applicable to all devices in the Stratix GX device family.
Figure C–1. Example Configuration
Stratix GX25F Device
PLD GX Transceivers
reset block TX PLL
reset block TX PLL
Reset Controller reset block TX PLL
IQ1
pll_areset reset block TX PLL
C–2 Altera Corporation Stratix GX Transceiver User Guide January 2005 Quartus II Software Messages
The following sections provide details on the feedback provided by the various versions of the Quartus II software when the design contains configurations 1, 2, or 3, described previously.
Quartus II Software to Version 3.0 SP2 This version of the Quartus II software allows configurations 1, 2, and 3, and provides no warnings. Because the behavior of the configuration is not modeled, differences in functionality exist between simulations and actual silicon.
Altera® recommends that you do not run the reset controller off the clock from the REFCLKB pin. This might result in the signals to the GXB being deasserted asynchronously (with respect to the clocks from the GXB). However, a serial link usually goes through an initialization phase. Therefore, metastability issues might not be critical because the logic has enough time to recover during initialization.
Quartus II Software Version 4.0 For configurations 1 and 2, the Quartus II software version 4.0 prevents the .sof file from being generated.
■ The assembler (ASM) will have an internal error (IE). Here are some of the messages from the Quartus II software log:
● Internal Error: Sub-system: ASM, File: asm_cdr.cpp, Line: 839, Illegal Clock Placement. Problem between Quad PLL and the Quad Clock Pad. PLL has Enable connected
● Internal Error: Sub-system: ASM, File: asm_cdr.cpp, Line: 840, Illegal Clock Placement. Problem between Quad PLL and the Quad Clock Pad. PLL has Reset connected
● Internal Error: Sub-system: ASM, File: asm_cdr.cpp, Line: 863, Illegal Clock Placement. Problem between RX Channel Resets and the Quad Clock Pad. All RXs in Quad have Resets connected
f Please refer to recommendation n in “Recommendations” on page C–5 if you have an existing design (including the board) and cannot make changes.
The Quartus II software version 4.0 supports configuration 3. There are no warnings and results vary from simulation to actual silicon.
Altera Corporation C–3 January 2005 Stratix GX Transceiver User Guide Known Issues
Quartus II Software Versions 4.0 SP1 & 4.1 For configurations 1, 2, and 3, the Quartus II software versions 4.0 SP1 and 4.1 provide an error message if the resets are used as described in those configurations. Unconstrained flows create a fit that does not have the clock pin reset problem or a no-fit if such a fit cannot be found. Quartus II software versions 4.0 SP1 and 4.1 provide an error message.
■ User assignments that force the previously discussed issues with clock configuration yield a user error during fitter operation.
Examples of the error messages from the Quartus II software log are shown below. These are generated for configurations 1 and 2.
■ Error: Can’t place GXB pin HSDI_CLK1_IN_I at location AM7 because of incompatible location or I/O standard assignments Error: Can’t place input clock HSDI_CLK1_IN_I at pin AM7 which is in the same quad as XGMII
■ Error: Can’t place GXB transmitter or receiver channels and/or their associated I/O pins due to illegal location or I/O standard assignments or inappropriate device Error: Can’t fit design in device
Figure C–2 shows an example of an error message.
Figure C–2. Error Messages
The following error messages are generated in the Quartus II software fitter for configuration 3.
■ Error: XGMII GXB_RX:GXB_RX_b|CUSTOM_RX:CUSTOM_RX_inst|altgxb:altg xb_component|xgm_machine[0] exists in a Quad that has no GXB Transmitters and has GXB Transmitter PLL GXB_RX:GXB_RX_b|CUSTOM_RX:CUSTOM_RX_inst|altgxb:altg xb_component|pll[0], but all the RXANALOGRESET signals are connected. This is not allowed.
C–4 Altera Corporation Stratix GX Transceiver User Guide January 2005 ■ Error: XGMII GXB_RX:GXB_RX_a|CUSTOM_RX:CUSTOM_RX_inst|altgxb:altg xb_component|xgm_machine[0] exists in a Quad that has no GXB Transmitters and has GXB Transmitter PLL GXB_RX:GXB_RX_a|CUSTOM_RX:CUSTOM_RX_inst|altgxb:altg xb_component|pll[0], but all the RXANALOGRESET signals are connected. This is not allowed.
f Refer to recommendation n in the section “Recommendations” on page C–5 if you have an existing design (including the board) and wish to keep the design.
Recommendations
The reset sequences described here are only recommendations. These recommendations are to guard against potential initialization issues. However, the transmitter PLLs within the transceivers are robust and should track the reference clock during a loss of lock conditions without requiring a reset. This reset signal must be used only if the PLLs fall into an unrecoverable state. During lab testing at the factory, the Stratix GX device did not require that the PLLs be reset. The PLLs have a wide pull in range and were able to relock to their respective reference clocks.
There might be situations where the read and write pointers in the phase compensation FIFO overlap. This will manifest as incorrect transmit data and in some cases, receive data. A digital reset should correct this error.
Here are the reset and clocking recommendations:
■ Do not run the reset controller off the clock from the REFCLKB pin. This might result in the signals to the GXB being deasserted asynchronously (with respect to the clocks from the GXB). However, a serial link usually goes through an initialization phase. Hence, any concerns of meta-stability issues may not be critical as the logic has enough time to recover during initialization.
To issue a pll_areset or pllenable or rxanalogreset (receive only) with configurations 1 or 2 using the Quartus II software version 4.0, use the following INI variable:
asm_skip_gxb_clock_fanout_restriction=on
For the Quartus II software version 4.0 SP1 (for configurations 1, 2, and 3), the setting in the Quartus II Settings File (.qsf) must be
set_global_assignment -name STRATIXGX_ALLOW_CLOCK_FANOUT_WITH_ANALOG_RESET ON
Altera Corporation C–5 January 2005 Stratix GX Transceiver User Guide Known Issues
The equivalent INI setting is
asm_skip_gxb_clock_fanout_restriction = on
If you use the INI variable, you are not required to make any changes to the QSF. When you use the QSF setting, the Quartus II software issues a critical warning if you implement any of the configurations (1, 2, or 3). This critical warning message warns that these clock and reset configurations are not modeled in simulation and there will be differences in behavior between functional simulations and actual silicon.
Figure C–3 shows an example of a critical warning.
Figure C–3. Critical Warning
The critical warning in this case warns you that the pll_areset signal will power-down the clock pad.
■ Do not use the pll_areset, pllenable, or rxanalogreset signals in receive-only configurations. The Stratix GX device is used in various systems and configurations. Based on the feedback and tests performed in the lab, assertion of any or all of these reset signals is not required for the PLLs to recover if they lose lock.
The pll_areset and pllenable signals are power-down signals Assertion of these signals powers down the entire transceiver block. rxanalogreset is also power-down signal. Assertion of this signal powers down the receiver. For more information about these signals, see the chapter Reset Control & Power Down.
C–6 Altera Corporation Stratix GX Transceiver User Guide January 2005 ■ You can use the REFCLKB pin on an unused transceiver block to bring in the clock. Altera recommends that you study the IQ routing to ensure that the transceiver block to be used can be reached from the selected REFCLKB pin. It might be possible to use the global clock pin for lower input clock frequencies. If the design requires using more than one transceiver block, there might be some restrictions because of the limited global clock resources. Please refer to the Stratix GX FPGA Family data sheet for more information on clocking resources available for each device in the family.
■ For designs that have receive-only configurations, try these solutions:
● While asserting rxanalogreset, ensure (if possible) that all four channels are not being reset at the same time. ● Do not use the transmitter PLL, train receive PLL from the receiver input reference clock (rx_cruclk).
You must carefully evaluate your design based on the recommendations in this appendix. Because you can configure the Stratix GX device in many different ways, there might be some configurations that are not covered by this document. Please contact ALTERA Applications for resolution on issues that are not addressed in this document.
Altera Corporation C–7 January 2005 Stratix GX Transceiver User Guide Known Issues
C–8 Altera Corporation Stratix GX Transceiver User Guide January 2005